Dunkerque |
|
| Career (France) | |
|---|---|
| Namesake: | City of Dunkirk |
| Laid down: | 24 December 1932 |
| Launched: | 2 October 1935 |
| Commissioned: | 1 May 1937 |
| Fate: | Scuttled 27 November 1942 |
| General characteristics | |
| Class and type: | Dunkerque class battleship |
| Displacement: | 26,500 tonnes |
| Length: | 215.1 m (705.7 feet) |
| Beam: | 31.1 m (102 feet) |
| Draught: | 8.7 m (28.5 feet) |
| Propulsion: |
6 Indret boilers 107,500 shp (designed) 135,585 shp (max) |
| Speed: | 29.5 knots (designed) 31.06 knots (max) |
| Range: | 7,850 nm at 15 knots 2,450 nm at 28.5 knots |
| Complement: | 1381 |
| Armament: |
8 x 330mm/50 Modèle 1931 guns in quadruple Mle 1932 turrets 5 x double 37 mm/50 CAD Mle 1933 turrets 8 x 13.2 mm/76 CAQ Mle 1929 Hotchkiss mountings |
| Armor: |
225 mm (side belt) 125-115mm (deck) 330-310mm (turrets) |
| Aircraft carried: | 4 hydroplanes Loire 130 |
The Dunkerque was the first unit of a new class of warships of the French Navy built in the 1930s, officially rated as battleships, or even «navires de ligne» (ships of the line), as Dunkerque and Strasbourg constituted, from the commissionig of Strasbourg to some days after Mers-el Kebir, the «1ère Division de Ligne». But they were often classified by maritime historians as «fast battleships», «little battleships»,[1] battlecruisers.[2]
Not as well-armed and considerably less armoured than contemporary battleships, they were nonetheless considered scaled-down battleships and were considerably more balanced (in the ship's performance tradeoffs between armour and armament) than battlecruisers. The Dunkerques were superior in all respects to the threat they were designed to counter, German pocket battleships of the Deutschland class, in effect scaled-up cruisers.
The design was innovative, having the entire main armament mounted forward in two quadruple turrets which gave unrestricted forward fire.
Contents |
In 1922, the Washington Naval Conference, concluded by the Washington Naval Treaty, decided to stop, for ten years, any new battleship building, as a new naval armaments race was developing, between the United States of America, the United Kingdom, and Japan, building or projecting respectively the Colorado[3] and South Dakota[4] class battleships, and the Lexington[5] class battle cruisers, the G3 battlecruisers,[6] the Mutsu [7] class and Tosa[8] class battleships and Amagi[8] class battlecruisers. The Treaty fixed for battleships to be built, the limits of 35,000 tons for standard displacement, and 406 mm (16-inches) for the main artillery calibre, and allowed the United States to complete three Colorado class battleships, Japan to complete two Mutsu class battleships, and the United Kingdom to build two battleships, respecting the limits fixed by the Treaty. France and Italy each were also allowed to replace, after 1927, two of their old battleships.[9]
Germany was not subject to the Washington Treaty limitations, but to specific stipulations of the Treaty of Versailles, and was forbidden to build any warship with a displacement greater than 10,000 tons.[10] This limit was less than the seize of the HMS Minotaur[11] armoured cruiser class, or of the SMS Schleswig-Holstein[12] pre-dreadnought, all built before 1910.
The United States, the United Kingdom, and Japan have used their rights resulting from the Washington Treaty, but neither France not Italy, due mainly to financial difficulties, but also because, even in naval circles, the interest of building battleships seemed very questionable,[13] · [14] as no decisive victory had resulted from a cataclysmic clash between battleships, since the American victories of Manila Bay and Santiago de Cuba, during the Spanish-American war and the Japanese victory of Tsushima, more than 24 and 17 years earlier.
The W W I experience had clearly shown the problem of ensuring the safety of maritime commercial roads, for which cruisers appeared better suited than battleships, so by the late 1920s, all the countries which had signed the Washington Treaty undertook the building of new heavy cruiser classes.[15]
So, in the early 1930s, the most powerful battleships had been designed before the Treatyof Washington, and were armed with four double turrets of 15-inches (381 mm)(Queen Elizabeth,[16] and Revenge[17] classes, and HMS Hood,[18] ), or 16-inches caliber (406 mm) (Colorado, and Nagato classes). The Nelson[19] class battleships themselves, built between 1922–1927, with three triple 16-inches turrets forward, were based on 1921 G3 battlecruiser concept. The top speed was, for most of them, of 21–24 knots (Revenge, Colorado, Nelson, Queen Elizabeth battleship classes), for a few ones of 27 knots (Nagato class battleships), with the notable exception, in Western waters, of the HMS Hood fast battleship, and the two Renown[20] class battlecruisers, whose speed exceeded 30 knots.
The French Admiralty, under Vice Admiral Salaün, discussed, in 1926-1927, of ships designed as «cruiser killers», able to outgun and outrun the Italian heavy cruisers, which were considered as the main threat against the maritime liaisons between France and North Africa,[21] as the first unit built, Trento, had been laid down in 1925, and launched in 1926. The French designers considered a displacement of 17,500 tons which would have allowed to build four units, respecting the maximum limit of 70,000 tons, which the Washington Treaty had fixed for the replacements authorized for France. An artillery arrangement of two 305 mm (12-inches) quadruple turrets forward was examined, combining the choice of quadruple turrets made by the French designers of the Normandie[22] and Lyon battleship classes and the «all forward» arrangement of the Nelson battleship class. The speed would have been of 34-35 knots, the armor able to resist to 203 mm shells. But, finally, such warships would not have been able to fight in the battle line against the old Italian battleships[23] · .[24]
In 1927, studies were undertaken of ships designed as battlecruisers of 37,000 tons. A «trial» displacement of 37,000 tons would have been the equivalent of a «standard» Washington displacement of 32-33,000 tons, near the maximum limit for battleship displacement fixed by the Washington Treaty. Two variants of draft drawings have been found.[25] Both show warships, up-scaled versions from the Suffren cruiser class, with a tripod foremast with the fire control director for the main guns atop, and two ranked funnels, the main artillery in three turrets, two fore and one aft, a secondary artillery of quad turrets of 130 mm against ships, eight single 90 mm Mle 1926 HA guns, twelve 37 mm Mle 1925 single AA mountings, and triple torpedo tubes. The aircraft installations would have taken place in the center of the ship, with a hangar after the bridge structure and two catapults abeam the second funnel. The propulsion machinery would have been constituted of two groups of boilers and turbines, as on the French cruiser Duquesne[26]
The 1927-1928 first variants would have had a main artillery of quad turrets of 305 mm, three quad 130 mm turrets, an armored belt of 220–280 mm thickness, and twelve Guyot-du-Temple boilers, developing 180,000 hp for a speed of 33 knots, with a hull of 254 m length, and 30.5 m beam. The 1928 second variant would have been rather a «fast battleship» than a battlecruiser, with a main artillery of three twin turrets of 406 mm, four quad 130 mm turrets, a shorter hull (235 m), with a sligthtly broader beam (31 m), a thicker armor, and only two thirds of the power of the 33-knots ship, for a speed of 27 knots.[26]
If there were some graving docks, as Brest Laninon docks, or Toulon Vauban grands bassins, completed in 1927, or Bizerta Sidi Abdallah dock, where it was possible to accommodate hulls of more than 250 m length, there were no Navy building docks to build such hulls, the Brest Salou n°4 dock was only 200 m long. In civil shipbuilding yards, only one liner, SS Île de France, 247 m long, whose maiden voyage occurred in 1927, had been built, in the Saint-Nazaire Penhoët yards. So, the building of 35,000 tons battleships was clearly outpassing the technical and financial capacities of the French Navy, as the building costs of the infrastructures would have been equivalent of those of two more battleships, and would have jeopardized the building programme of the other categorizes of warships, cruisers, destroyers, and submarines.[27]
Moreover, in the same time, discussions at the Disarmament Subcommittee of the League of Nations had begun in Geneva, about the pursuit of naval armaments limitation policy. The United Kingdom was trying to obtain more drastic limitations than those of the Washington Treaty, as 25,000 tons for battleship maximum displacement, and 305 mm for battleship maximum caliber, and the French Government did not wanted to jeopardize these negociations.
The Service Technique des Constructions Navales (S.T.C.N.), French equivalent of the Department of Director of Naval Construction, studied in 1929, on the request of Vice Admiral Violette who has become Chief of Staff of the French Navy in 1928, the concept of a «protected cruiser», with a displacement of 23,690 tons, three 305 mm turrets, one triple and one quad fore, one triple aft, four twin 138 mm mountings, caliber used on the most recent destroyers, eight double turrets of 100 mm AA, as on the last heavy cruiser, Algérie. The speed would have been of 29 knots, and the armor able to resist only to 203 mm shells. But the general layout is interesting, as it is no more reminiscent of the cruiser Suffren, but of the latter cruiser Algérie, with a distinctive forward tower and a single funnel well abaft the forward tower, anticipating the profile of the latter Dunkerque.[27]
Everything changed when, in February 1929, the German Reichsmarine laid down the keel of Deutschland, an «armoured ship» (in German Panzerschiffe), of 10,000 tons displacement, respecting formally the limitations of the Treaty of Versailles, actually at least 25 % heavier but this was not known at this moment. With two 280 mm (11-inches) caliber triple turrets, and a speed of 26 knots, this ship outgunned every so-called heavy cruiser with their 203 mm (8 inches) guns intended to respect the limitations of the Treaty of Washington, concerning the caliber of cruiser main artillery, and outran every battleship, except the three fastest British units, HMS Hood, HMS Renown and HMS Repulse.[28]
The type of Deutschland was commonly designated as a «pocket battleship», being actually as her German denomination indicated well, an «armoured cruiser».[29] The use of welding instead of riveting for the hull, in order to save weight, the diesel propulsion, which assured a longer radius, and the stipulations of the Treaty of Versailles, without a caliber limit, have enabled the Reichsmarine to build a warship that most experts thought inconceivable, and which revealed itself as a dreadful threat for the commercial maritime roads in Eastern Atlantic.
The reaction of the French Admiralty was to prepare draft drawings for a ship which would outclass the German "pocket battleship", in armament, armor and speed. It appeared that the armament of the French previous projects might be retained, that the speed might be of 30 knots, and not necessarily superior, but the most important feature was that the armor had to be thicker to resist to 280 mm shells. These considerations were leading to a displacement of about 23,000 to 25,000 tons, which fits the maximum displacement that the United Kingdom found suitable in the naval armament limitations negociations.
The 1930 London Naval Treaty decided that the ten-years «battleship holiday» agreed at Wahington would be extended for further five years, until 31 December 1936. France and Italy may, however, build the remplacement tonnage which they were entitled to lay down in 1927 and 1929 in accordance with the provisions of the Treaty of Washington. Nevertheless, France and Italy refused to adhere to any more qualitative limitations, which were mainly concerning cruisers. France argued that ship construction had just started in Germany of the armour-clad Deutschland, and following the rejection of the agreement by France, Italy was no longer prepared to accept new restrictions[30] · .[31]
In order to establish an agreed ceiling to new naval construction, bilateral talks took place between France and Italy, with the great encouragement of the United Kingdom, at the very beginning of 1931, and a «basis of agreement» was concluded on March 1, 1931. Up to 1936, both countries would have been allowed to build only two battleships each of 23,333 tons. But it was not possible to go further, as the Regia Marina was not satisfied of the 23,333 tons battleship Italian project,[32] with three twin 381 mm turrets, and a profile reminiscent of the heavy cruiser Pola, then in construction[33]: a very complete refit of the artillery and power plant of the Conte di Cavour battleships class[34] will begin in 1933, and the ship designers might focus on on the 35,000 tons battleship studies.
However, in 1931, the French Admiralty explicitely confirms the choice of the battleship of 23,333 tons, as the battleship of 17,500 tons would have been too lightly armored, and the battleship of 35,000 tons would have required technical and financial capacities that outranged the possibilities of France. This battleship of 23,333 tons would have had a 213 m length, with a 27.5 m beam, two quad 305 mm/55 cal turrets forward, three quad 130 mm turrets Dual Purpose aft, a speed of 30 knots, an armored belt of 230 mm, and an horizontal protection of 150 mm. But when this proposal was submitted to the Parliament, in May 1931, the discussion lasted two months, with much criticism, as it was difficult to understand why it was necessary to have a displacement double of the warship which was to be countered, and why it was not preferable to build a 35000 tons battleship. So, in the 1931 Estimates, in July, funds were allocated only for further studies, with the proviso that the final characteristics should be subject to a thorough revision, the results of which would have to be submitted to the Parliament, before passing any building orders. Then, Vice Admiral Durand-Viel, the new Chief of Staff of the French Navy from January 1931 , requested further studies for upgrading the main artillery caliber, from305 mm to 330 mm, to outgun the Italian battleships.
This resulted to an increase in displacement to 26,500 tons, a 2-meter increase in length, a 2.5-meter increase in beam, a slight reduction in maximum speed to 29.5 knots, the substitution of 330 mm/52 guns to 305 mm/55 ones, two more double 130 mm DP turrets, and a slight increase of the armor, in the armored belt, as on the armored decks[35] · [36] In early 1932, the project was approved by the Parliament commitees, and the Minister of Defence, François Pietri, succeeded to include it in the 1932 Estimates. So emerged the Dunkerque,[37] which was ordered on October 26, 1932, and laid down on December 24, 1932.[35]
On February 14, 1934, two German battleships (or battlecruisers) were ordered, but were laid down more than onr year later, Gneisenau was laid down on May 6, 1935, and Scharnhorst, on June 15, 1935. Originally, they were intended to be the fourth and fifth units of the Deutschland class. But to counter the Dunkerque class, the need of stonger warships led to conduct secretly (as Adolf Hitler announced the rearmament of Germany in violation of the Treaty of Versailles only in 1935) studies for a new design, influenced by the Ersatz Yorck battlecruiser, planned in 1915.[38] Finally they emerged as a kind of «little battleship» class, as her displacement was substantially under the maximum limit fixed by the Treaty of Washington, but with armament sacrified to speed, not to armor. They were heavier (31,800 tons) than the Dunkerque class battleships, better armoured (with an armored belt of 350 mm thickness, more than of the latter KMS Bismarck), but armed only with nine 280 mm guns, the same caliber as the Deutschland class. A heavier caliber had been considered for the main artillery, and would have been preferred by Adolf Hitler, as the Dunkerque class battleships were armed with 330 mm guns. But when the final design of these ships was about to be settled, Germany was negotiating the 1935 Anglo-German Naval Agreement, and the British Government was pressing very strongly for a limitation on the battleship main artillery caliber. So reluctantly, an improved gun, with longer barrel, higher muzzle velocity, but the same 280 mm caliber was chosen.[1]
As the French Navy ship designers believed that Dunkerque class battleships' armor was able to resist to 280 mm caliber shells, there would not have been any necessity to conceive an heavier battleship class. But Duce Benito Mussolini announced, on May 26, 1934, the decision to fully use the global tonnage allocated to Italy by the naval Treaties to build battleships, and on June 11, the Stefani news agency indicated that two battleships would be laid down with a 35,000 tons displacement, the first ones since the Treaty of Washington.[39]
The time had occurred to build the first French 35 000 tons battleship. But time was missing to achieve a design for a new heavier battleships class. The French Navy Board, on June 25, 1934, recommended, unanimously, to not modify the 1934 Naval Program, and to order the building of a Dunkerque's sister ship, improving the vertical armored protection: Strasbourg laying down was ordered on July 16, 1934.[35] It will be the last French battleship with a displacement of less than 35,000 tons.
Dunkerque with a «standard» displacement of 26,500 tW («normal» 31,400 tons), a 215 m length, a 31 m beam , and a 8.5 m draught, had a design very innovative, notably the whole of the main armament (eight 330mm/50 Modèle 1931 guns) mounted forwards in quadruple turrets. Her propulsion machinery was developing normally 107,000 shp, for a speed of 29.5 knots. Her armored belt had a maximum thickness of 241 mm (9¾-inches).[40]
The weight distribution [41] was as follows .
| Parts of the ship | Hull |
Fittings | Artillery | Artillery protection |
Hull protection |
Propulsion plant |
Fuel | Total |
|---|---|---|---|---|---|---|---|---|
| Weight | 7,011 t | 2,767 t | 4,858 t | 2,676 t | 8,364 t | 2,214 t | 2,860 t | 3,0750 t |
| Percentage | 22,8 % | 9 % | 15,8 % | 8,7 % | 27,2 % | 7,2% | 9,3 % | 100 % |
Eighteen months before Dunkerqe has been laid down, the United Kingdom, on March 15, 1931, had to decommission, to scrap her, the last glorious veteran of Admiral Beatty's Battlecruiser Fleet, at the battles of Dogger Bank and Jutland, the battlecruiser HMS Tiger, because of the limitation of the number of British battleships to fifteen, imposed by the Treaty of London. Her characteristics were similar enough to the Dunkerque ones, armament eight 13.5-inch (343 mm) Mk V guns, displacement 28,500 long tons (29,000 t) (normal), length 660 ft (201.2 m), beam 90 ft 6 in (27.6 m), draught 32 ft 5 in (9.9 m), power 108,000 shp, speed 29 knots.[42] This similaririty explains the opinion of Henri Le Masson who considered that the Dunkerque class warships «were more of a battlecruiser type than real battleships».[2] The main difference was the arrangement of the main artillery, on Dunkerque, with two quadruple turrets instead of four double ones, saving 27% weight on turret armoring,[37] while retaining the same hitting power. Dunkerque was fitted too with a twenty-years more modern propulsion plant, as HMS Tiger was the last Royal Navy warship to have coal fired boilers, and she had been fitted, against the advice of her designer, Sir Eustace Tennyson d'Eyncourt, with large-diameter-tubes boilers instead of more modern small-tube boilers.[43] All this allowed Dunkerque to carry a 10 cm thicker armor, on the turrets faces (330 mm versus 229 mm), and on the horizontal armored decks.
But several key features of the Nelson class battleships might be found inspiring the Dunkerque French designers : locating the machinery aft saved on shaft length and therefore on weight, the inclined armor belt was equivalent to a thicker vertical belt, a secondary battery in twin turrets aft had superior firing arcs, a tower structure carried the main fire control directors. But these two battleship classes differed both considerably in their general layout, as the Nelson battleship class did not yield anything in terms of hitting power ( with the most powerful main battery, compared to US or Japanese battleships) and protection (with the thickest armored belt and decks), but accepting a relatively slow speed, as Dunkerque battleship class was designed as a «balanced» project in terms of hitting power and protection, the priority beeing a speed reaching 30 knots, with a displacement not exceeding the Naval Treaties limits less 10,000 tons. But the difference between Dunkerque and the previous French projects may also be considered as reflecting the evolution from the Suffren cruiser class to the cruiser Algérie.[44]
The quadruple arrangement had been foreseen for the French Normandie and Lyon class battleship projects, just before W W I. The «all forward» main artillery arrangement had been first introduced by the Royal Navy on the Nelson class battleships, but these warships had three turrets carrying nine guns and the angles of fire for the rearmost were limited by the turrets in front, as it had not seemed possible to accept the supplementary weight of armor, above the main armored deck, for the barbette of a third turret in superposition of a second turret yet raised.[45]
Retained on Dunkerque, the two quadruple 330 mm fore turrets arrangement gave unrestricted forwards fire. So, the entirety of the main artillery was able to fire forwards, as the ship closed in to her enemy, in an angle where she made the smallest possible target. When Dunkerque was laid down, it was more powerful than any German or Italian existing warships, and she was intended to be engaged as part of a scout wing of the slower and heavier British battlefleet, so the concept of the main artillery concentrated in bow seemed justified. Six years later, the opinons had changed, and the French Admiralty came back to a main artillery arrangement on bow and stern, on the Gascogne battleship project, and in 1940 June in the tactical situation of the battle of Mers-el-Kebir, this main artillery disposition on the French modern battleships was actually a severe handicap.
The drawback of the quadruple turret was that a single unlucky shot immobilising one of the turrets would effectively put half the main artillery out of action. So the French quadruple turrets of both Dunkerque and Richelieu class battleships, were divided internally to localise damage,[40] and this was proved effective when Dunkerque, at Mers-el-Kebir, was stricken by a 381 mm shell on the upper 330 mm turret, which put out of action only the right half turret.[46]
In order to avoid that one unlucky hit damages both turrets together, they were positioned 27 m apart from one another,[35] as there were 19 m between the A and B turrets, and 23 m betweeb B and C turrets of the Nelson class battleships.[47]
The diameter of a barbette is all the more large because of the number of the turret guns, and their caliber. With a 32 m beam, the Nelson class battleships supported barbettes for three 406 mm guns turret. The 1911 French designers of the Normandie battleship class had thought that it was possible to install quad 340 mm turrets on ships with a beam of 27 m. The Dunkerque designers resolved that quad 330 mm turrets were the maximum possible with 31 m beam. Nevertheless, the four barrels were not mounted independently in individual mounts because this would have meant an unduly large barbette diameter. For that reason the right and left hand pair of barrels where placed in a common mount each.[37] It was not the case on the fore and aft 14-inches quadruple turrets of the British HMS King George V class battleships, which had a 34 m beam. On Dunkerque and Strasbourg, as later on Richelieu and Jean Bart, the guns of the half turrets were so close (1.69 m) that a wake effect between shells fired simultaneously by a half turret was leading to an excessive dispersal,[48] which has not been corrected before 1948 on the Richelieu battleship.[49]
The weight of one quadruple 330 mm turret, built by Saint-Chamond was 1,497 tons, nearly the same weight of one triple 381 mm turret of Littorio. The maximum gun elevation was of 35°, the muzzle velocity 870 m/s, and the range, at the maximum elevation, was 41,500 m which means that the trajectory was flat enough. The rate of fire was one round every 40 seconds (1,5 rounds per minute), and even every 30 seconds (2 rounds per minute). The turrets were intended for loading at any elevation angle, but as it occured that shells jammed in the breech at the higher elevations when the other guns were firing, practically, loading took place at 15° elevation. The rate of elevation was 6°/s, and the rate of train 5°/s.
The 330 mm shell was 1,65 m long, and weighed 570 kg, nearly twice the weight of the 280 mm Deutschland shell (300 kg), or of the Scharnhorst AP shell (336 kg).[50] The weight of Italian battleship shells was 452 kg for the 305 mm guns, and 525 kg for the 320 mm guns, after reconstruction.[51] The British battleships which bombed the French battleships at Mers-el Kebir have fired 875 kg shell.[52] The 330 mm shell was Armor Percing Capped (APC), registered in the French Navy as Obus de Perforation Modèle 1935 (OPf Mle 1935) existing in two variants, OPf and OPfK, the later OPfK variant incorporating a dye bag and fuze (dispositif K) to colour ( red in Dunkerque and green for Strasbourg) not only splashes but hits, thereby facilitating spotting for ships operating in formation while in combat. A Highly Explosive (HE) variant of shell, referenced OEA Mle 1935 (Obus Explosif en Acier), could have been designed and tested, but would have not been ordered, as no reference of this shell has been found in the war ammunition inventories of the ships.
The heavy guns caused a great deal of difficulty: when firing slightly aft of a beam, the ship's command position was troubled by the noise of the explosion, the fire and the smoke to such an extent that the full arc of fire could not be utilized. The absorption of the great recoil forces by the ship's members also presented difficulties, and these ships which perforce had to be very lightly constructed , suffered tepeatdly from damage caused by firing their own guns[37].
The secondary artillery was dual purpose, anti-ship and long-range anti-aircraft, for the first time on capital ships, as the French Navy was followed by the Royal Navy on the King George V class battleships.[53] Three quadruple armored turrets (turrets V, VI, and VII), weighing 200 tons, were aft, one axial (turret VII) on the aircraft hangar, the other (turrets V and VI) laterally disposed, abeam the after superstructure. Like the 330 mm turrets, the quad 130 mm turrets had a 20 mm steel bulkhead dividing the turret in two independent half turrets, in which the two guns were placed on the same mount with a distance apart gun axes of 0,55 m. The two double turrets (turrets III and IV) amidships had only 20 mm anti-splinter plating[54].
In the anti surface mode, the 130 mm guns were firing 33.4 kg Semi Armored Piercing (SAP) shells (referenced in the French Navy OPfK 130 mm Mle 1933), with a muzzle velocity of 800 m/s, to a maximum range of 20,800 m, at the elevation of 45°, against aircraft, 29.5 kg time-fuzed HE shells (OEA Mle 1934), with a muzzle velocity of 840 m/s, with a ceiling of about 12,000 m at the maximum elevation of 75°. The rate of fire was 10-12 rounds per minute. The maximum training speed was 12°/s, and the maximum elevating speed was 8°/s.[55]
But these guns had a too weak caliber for their anti-ship mission.[56] The 130 mm (5.1 inches) guns had been used in single mountings (Mle 1919 and 1924), as anti-ship battery on the destroyers of Chacal and L'Adroit classes, commissionned in 1926-1931 but the later Guépard, and Le Fantasque classe destroyers , commissionned after 1929, were fitted with stronger 136.8 mm (5.5 inches) guns, also in single mountings (Mle 1923 and Mle 1927). The 1929 «protected cruiser» project was designed with anti-ship 138.6 mm LA guns, in dual mountings, which were actually installed (Mle 1934) for the first time on the Mogador class destroyers, in the very late 1930s years. In the Axis navies, the Kriegsmarine or the Regia Marina, which have fitted their battleships with distinct batteries for anti-ship and anti-aircraft purposes, have prefered the 150 mm caliber for the anti-ship artillery, on Scharnhorst, and Bismarck battleship classes or the 152 mm/55 Model 1934 or 1936 on Littorio class battleships.
In the anti-aircraft mode, the 130 mm Mle1932 guns were considered as having a poor efficiency against close rapid aircraft, as dive bombers, due to its too slow rate of fire (10 rounds per min).[56] The US Navy or the Royal Navy which opted for dual-purpose batteries, chose calibers equivalent of the French 130 mm caliber, slightly less, 127 mm (5 inches) for the US Navy, or slightly more, 133.3 mm (5¼ inches), for the Royal Navy. The US Mark 12 127 mm/38 caliber gun, used in dual mountings on North Carolina and South Dakota class battleships, and Essex class aircraft carriers, and many cruisers, had an higher rate of fire, 15 rounds per minute, and even 22 rounds per minute, during short periods. But it was usually under the control of the advanced Mark 37 Gun Fire Control System which provided accurate and timely firing solutions against surface and air targets. The Royal Navy 133.3 mm DP guns, first used on the King George V class battleships, and later on the Dido class cruisers, had, originally, characteristics equivalent to French 130 mm guns, but they were found performing only , on the last unit of the King George V battleship class, HMS Anson, or on the Bellona sub-class cruisers, when they will have been linked to improved RP10 and RP10Mk2 control which increased training and elevating speeds to 20°/s, and with the High Angle Control System in its most performing versions. Dunkerque class battleships were the first French capital ships to have Remote Power Control (RPC) for trainig and elevating, on the main and secondary turrets, but the Sauter-Harlé-Blondel RPC training gear proved unreliable, and the system never worked properly.[44] A so-called «electromagnetic detection device», the French ancestor of radar, will have been fitted on Strasbourg in 1942,[57] as on Richelieu (as early as 1941),[58] and Jean Bart,[59] but only for sea or air warning, not as gunnery fire control radar.
With five 37mm CAD Mle 1933 semi-automatic mountings and eight 13.7 mm machine-guns quadruple mountings, these ships lacked the numerous quick-firing light artillery which was mounted on the Richelieu, during her refit.
The 37 mm/50 guns were frequently used as light anti-aircraft battery on the French Navy warships, in the late 1920s. In single mountings CAS Model 1925, they were fitted on the 10,000 tons heavy cruisers and destroyers. Hand-loaded, using 6-round box magazines, even in the twin semi automatic CAD Model 1933, the rate of fire which intended to be of 20 to 30 rounds per minute, was practically of 10 to 15 rpm. This appeared to be too slow, comparing with the RoF of guns of equivalent caliber, as the British Pom Pom gun, or the Swedish designed Bofors 40 mm/L60 gun, the rate of fire of those being 120 to 200 rpm. So it was decided to develop a new gun 37 mm/70 Model 1935, with an automatic AA twin mounting (ACAD Model 1936), linked with one fire control director (or two montings for one FCD). The intented rate of fire was 165-172 rpm.[60] But the development of the gun and its twin automatic mounting was more difficult than previewed, and it appeared that it would not be possible for the Dunkerque to be fitted with before her completion.
During her trials, Dunkerque received only six 13.2 mm/76 quadritubes Model 1929 Hotchkiss mountings, amidships and abeam tower. At the time of completion she was fitted with six single 37 mm CAS Model 1925 mountings which were replaced, in early 1939, by four twin semi automatic 37 mm CAD Model 1933, two abeam turret II and two between the funnel and the aft tower, with four directors, two above the fore pair of 37 mm mountings, and two just before the second pair. A fifth 37 mm CAD Model 1933 was added, in August 1939, abaft the 130 mm quad turret VII (centerline aft).[61]
A massive fore control tower was, for the first time, fitted with a internal lift, and topped by three conductors ( n°1, 2, and A, top down) mounted on the same axis. The accumulation of heavy weights high up in the top (85 tons) was noteworthy.[62] When Dunkerque was torpedoed at Mers-el-Kébir, on July 6,1940, this proved to be a shortcoming as the main fire control directors were unseated from their ball races, because of the whiplash effect on the mast around which they were mounted[63].
A secondary control tower, topped by two conductors (n° 3 and B), was positioned abaft the funnel.
For the 330 mm battery, there was a stereoscopic triplex 12 m OPL (Optique de Precision de Levallois-Perret) range finder, replaced in 1940 by a 14-meter model, in the director A which was weighing 40 tons, 30 m above the waterline, in lower position atop the fore tower, a stereoscopic duplex 8 m OPL range finder in the director B, in lower position atop the aft tower, and two stereoscopic duplex 12 m OPL range finders, one in each main artillery turret. For the 130 mm battery, there was a stereoscopic duplex 6 m OPL range finder, for the anti-ship gunnery, in the director 2 which was weighing 25 tons, in central position, and a stereoscopic duplex 5 m OPL range finder for the anti-aircraft gunnery, in the director 1 which was weighing 20 tons, in upper position, both atop the fore tower, a stereoscopic duplex 6 m OPL range finder in the director 3, in upper position atop the aft tower, and three stereoscopic duplex 6 m OPL range finders, one in each quad 130 mm turret. Two stereoscopic SOM( Société d'Optique et de Mécanique de haute précision) 3-meter rangefinders were mountedon the sides of the fore tower, for night fire.
In addition to the main gunnery directors, a stereoscopic OPL 5-meter tactical rangefinder, to be used by the flag staff, was located, on Dunkerque, atop the conning tower.
For the optical watch, at the lower level (ville basse), for close sea targets, there were three lookout positions port and starboard, on the first deck abeam the bridge. For the aerial targets, the middle lookout station (veille moyenne) was on plaform 3 of the forward tower with five lookouts on either side of the ship. against mines and torpedoes, the upper lookout station (ville haute) was on platform 8 of the forward tower, with five lookouts on either side of the ship.
For night firing, there were seven searchlights projectors, four on a raised platform around the after base of the funnel, two on platform 6 on the rear of the fore tower, and one on forward position on the same level of the tower.
The aircraft installations (hangar, catapult and crane) on Dunkerque were particularly complete and well designed and were a major advance on the facilities installed in the older battleships in the 1920s, as the fast battleship which has been fitted in 1929 with a catapult on stern, removed in 1932 as it was frequenly awash in the North Atlantic heavy seas, because of the lack of freeboard aft.
A single 22 m long trainable catapult was located on center line, on the quaterdeck. It was operated with compressed air, and could launch a 3.5 tons aircraft at 103 km/h. Adjacent to the hangar there were workshops for repair and maintenance.
The aircraft were hull seaplanes Loire 130 type, single-engined (720 hp Hispano-Suiza 12-cylinder liquid cooled) with a 3,500 kg weight, a 210 km/h maximum speed, 165 km/h cruise speed at 1,500 m, two 75 mm MG and two 75 kg bombs. Two planes were to be stowed, wings folded, in a two tiers hangar, on the two platforms of a lift, and one on the catapult, wings deployed, with the possibility to stow a fourth plane atop the aviation hangar. The planes were moved on rails from the hangar to an elevator where they were placed on the catapult. At the end of its mission, the Loire 130 landed on the sea and then taxied alongside. It was lifted aboard by a recovery crane with a capacity of 4.5 tons.
The aviation fuel was stowed in tanks located in the upper part of the stern, with safety features, including the replacement of usued fuel by an inert gas, refrigeration and sprinkler systems.
The proportion of the protection relative to the design displacement reached 35.9%[41] which was the highest value recorded until then, as the armor weight was only 34 % of the design displacement on the Nelson class battleships[64].
The armor protection of the class was also very modern, as it used the "all or nothing" armor scheme, unlike contemporary German warships. The citadel about 126 m long corresponded to about 60% of the ship's length, very similar to the 57% of the Nelson battleship class, but left unprotected a long forward part of the ship.[62]
The underwater protection consisted in a «sandwich» of void spaces, light bulkheads, liquid loading compartments or compartments filled with rubber-based water-excluding compound (ébonite-mousse), and a heavy internal holding bulkhead to absorb the explosion of a torpedo head. The compartment outboard of the inclined armor belt had a maximum depth of 1.5 m, and had a filling of ébonite mousse. Inboard this compartement, there was a 16 mm bulkhead, inclosing a void compartment 0.9 m deep, then an oil fuel bunker 3.9 m deep, then a 10 mm bulkhead, containing a void compartement 0.70 m deep, backed by a 30 mm torpedo bulkhead of special steel. Abeam the magazines fore and aft, the torpedo bulkhead thickness was increased to 40-50 mm, and the fuel bunkerswas replaced by a same depth compartment, with a filling of ébonite-mousse. The maximum depth was around 7.5 meters. This figure was exceding the depth of underwater protection on existing battleships, where it was no more than 5 meters[65].
This underwater protection proved to be effective enough, when, at Mers-el-Kébir, on July 6, 1940, fourteen of the forty-four depth charges carried on the patrol ship Terre-Neuve, equivalent to 1,400 kg of TNT or eight air-launched torpedo warheads, exploded a few meters of Dunkerque hull.
The speed of a warship depends not only of the power of her propulsion plant, but also of her hydrodynamism, which varies with the ratio lenght/beam. But the lenght of the ship has consequences on the displacement, because of the weight of the hull itself, but also of the weight of the hull armor. With a main armament of eight twin 15-inch (381 mm) guns turrets, HMS Hood had a 42,000 tons displacement, a 262 m hull, a propulsion machinery developing 144,000 shp, for a 31 knots speed. The Nelson class battleships had a more powerful armament but with a weight-saving arrangement of triple turrets on a shorter «citadel», and a stronger protection. But her displacement was limited to 35,000 tons, so the hull was only 216 m long, and with a machinery space reduced, the propulsion plant power of 42,000 shp allowed only a 23 knots speed. The requirements imposed to the French designers of Dunkerque were different : a 26,500 tons displacement, allowing to accommodate an armement and a protection able to counter the Deutschland class «pocket battleships», but a 215 m hull which could be built, for its longest part (200 m), in the building dock of Brest Navy Yards and, imperatively, a speed of 29.5 knots.
The propulsion was assured by six Indret boilers, and four Parsons turbines, on Dunkerque. These small-tube boilers were operated at a pressure of 27 kg/cm² (350°C). They were 5;33 m long, 5.34 m high, and 6.50 m wide, installed two boilers side by side in three boiler rooms. Boiler Room1 was underneath the fore tower, with, from starboard to port, boilers n°10, and n°11, followed by the forward Engine Room housing the geared turbines for the wing shafts. Boiler Rooms2 and 3 were adjacent beneath the funnel, with boilers n°20, n°21, in BR2, and boilers n° 31 and n°32, in BR3. The after Engine Room housing the turbines for the center shafts, was abaft the Boiler Rooms2 and 3. A 18 mm bulkhead separated the forward Engine Room from the Boiler Room 2, dividing the machinery plant in two independant units. This «unit machinery» layout considered essential for relatively lightly-armored ships to enable them to continue operating following action damage was first introduced by the French Navy on the first Treaty cruiser Duquesne.
In each Engine Room, there were two sets of turbines, each driving a three-bladed propeller with a diameter of 4,20 m. Each set comprised a two High Pressure (27 kg/cm²) turbines (HP1 and HP2), a Medium Pressure (8.5 kg/cm²) turbine and Low Pressure forward and reverse turbines which were linked in series with HP 1 as a cruise turbine. The ship could steam at 15.5 knots on two shafts, and 20 knots, on four, at one quater power, HP 2 being engaged at between 34 and 50% of maximum power. Four turbo generators of 900kW each were distributed between the engine rooms.
Designed horse power was 107,000 shp for 29.5 knots. During speed trials, in May 1936, 30 knots were sustained during eight hours, with 114,000 shp, and a 30,000 tons displacement, and 31.6 knots were reached with 135,585 shp forcing.
The maximum fuel load for peace-time cruising was 4,500-5,00 tons, but in wartime, this figure was reduced to 3,700 tons, to maximise the effectiveness of the underwater protection system, as filling the liquid loading compartments to the brim create additionnal pressure on bulkheads, instead of absorbing the pressure of explosion.The radius was 7,850 nmi at 15 knots, 6300 nmi at 20 knots, and 2,450 nmi at 28.5 knots[66].
During the sea trials, it appeared that the funnel smoke interfered with the use of the aft control tower range finders, so the Dunkerque was fitted, between March and May 1938, with a more important funnel cap, nicknamed as a "bowler hat". War service showed that the ship's bow suffered damage in the rough seas of the North Atlantic winter, one of her Flag Officers speaking dedaignously of "hull from trying carene pool".[48] The German Scharnhorst class battleships had the same problem, particularly during the winter 1939-40, even after they had been fitted with a reinforced "Atlantic bow" in 1938-39.
The Dunkerque class battleships seemed to have been relatively lightly built, so she suffered damage from the blast, the noise, the smoke and the recoil of her own 330 mm guns firing,[37] and as noted above, the excessive closeness of the barrels of the two pairs of one quadruple turret caused an excessive dispersal of the shells of the same salvo.[48]
Dunkerque was laid down in the Brest Navy Yard, on December 24, 1932, in the Salou graving dock n°4. She was floated out on October 2, 1935, and the ship with 17 meters missing, as the graving dock was only 200 m long, was towed to Laninon graving dock n°8, where her bow was fitted. Sea trials were carried out from mid-April 1936 to late April 1937. In mid-May 1937, she represented France to the Naval Review of 1937, at Spithead, Portsmouth, to mark the coronation of King George VI. On May 27, a further review took place off the Isle of Sein, where the French Mediterranean and Atlantic squadrons were assembled following combined exercises. Dunkerque hosted there the Navy Minister and the new Chief of Staff of the French Navy, Vice Admiral Darlan[67] · [68]. On September 1,1937, Dunkerque joined the Atlantic Squadron, as flag ship of C.in-C., Vice Admiral Gensoul, and take part in 1938 to various exercises with the Atlantic Squadron.
From 1939, Dunkerque and Strasbourg, with some cruisers and large destroyers formed a fast warships naval force, called Force de Raid. Based in Brest, Dunkerque was its flagship.
In the first days of September 1939, the Force de Raid, under Vice Amiral d'Escadre (Squadron Vice Admiral) Gensoul on Dunkerque, including the 1 st Line Division, the 4th Cruiser division, and eight large destroyers was based in Brest, and sortied immediatly, as German «pocket battleships» were reported, wrongly, to try passing in the Atlantic. But it was soon decided to split the Force de Raid, in hunting groups against the German surface raiders, incorporating Royal Navy warships.
In November-December, Dunkerque and the French 4th Cruiser Division, joined HMS Hood to intercept, under orders of Vice Admiral Gensoul, Scharnhost and Gneisenau, which had sunk the Armed Merchant Cruiser HMS Rawalpindi, north of Faroe Islands on November 23, 1939. As the German battleships renounced to break into the Atlantic, Dunkerque suffered bow damages, in a huge North Atlantic tempest and had to be docked for repairs.[48] Dunkerque, on December 1939, took part in the shipping to Canada of a part of the Banque de France's gold reserve.[48]
Face to the dubious Italian attitude during the spring 1940, the Force de Raid was despatched, on April 2, 1940, to the Mediterranean, but was ordered to return to Brest, some days later, to cover the Allies' reaction to the German landings in Norway, on April 9,1940. Finally the Force de Raid was definitively transferred to Mers-el Kebir since April 24, 1940.[69]
The only test in battle for the Dunkerque came in the attack on Mers-el-Kébir on July 3, 1940, from the Force H battleships, HMS Hood, HMS Revenge, and HMS Valiant, sent to coerce the French battleship squadron to join the British cause. By then, she had not been designed to fight with such powerful battleships.
As the old super-dreadnought Bretagne capsized and sank, killing nearly 1,000 sailors, the Dunkerque was painfully breaking her mooring ropes. She quickly suffered four 15 inch shell hits, the first rebounced on the upper 330 mm turret roof, killing all the men in the right half turret as the left half turret remained operational, the second damaged the aircraft installations, the last ones passed through the 225 mm armored belt, which had not been designed to resist 15-inch (381 mm) shells: the third one penetrated the handing room of starboard twin 130 mm turret and put out of action the forward turbine room, as the fourth one severely damaged the central boiler room (BR 2). Thence the ship had to be beached on the other side of Mers-el-Kebir roadstead.[46]
The damage was not as deadly as it might have been feared, because the British fire ceased after less than twenty minutes, the French admiral having signaled that he had ordered his ships to cease firing, and because the ship could have been beached. Then Admiral Esteva, Admiral Sud (C. in C., French Navy in North Africa, at Bizerta) told in a later radio message to the French Admiralty of "moderate" damages[70], and/or boasted, in a communiqué to the Algerian press, that Dunkerque would soon be able to return to Toulon on her own steam[71]. Knowing this, the British Admiralty ordered Admiral Somerville, Force H Flag Officer, to attack again, to put Dunkerque permanently out of action.
Dunkerque being beached just in front of a village, Admiral Sommerville, fearing that gun fire might cause serious collateral damages to civilians, preferred to attack with torpedo bombers on July 6. Unluckily, one of the torpedoes hit the small patrol ship Terre-Neuve, carrying depth charges alongside Dunkerque. The explosion of fourteen depth charges, equivalent of 1,400 kg of TNT, or eight air lauched torpedo warheads ripped an enormous hole in the battleship's hull, killing a further 40 sailors, and Dunkerque sank in shallow water[72]. The ship escaped probably to a total loss, as the flooding of the 330 mm gun magazines had been ordered as soon as the torpedo-bombers appeared[71]. The total number of killed on Dunkerque during the two attacks of July 3 and July 6,1940, reached 210.
After being refloated and temporary repairs completed, Dunkerque returned to Toulon in February 1942. She was in armistice custody, disarmed and in drydock.
After the Wehrmacht has occupied the Zone libre in retaliation for the successful Allied landings in North Africa, she was scuttled on November 27, 1942[73], when the Germans attempted to seize the French warships remaining under Vichy control. Her commanding officer, Captain (Capitaine de vaisseau) Amiel, initially refused to sink his ship without written orders, but was finally convinced to do so by the Commanding Officer of the nearby light cruiser La Galissonnière. Demolition charges were ignited, destroying the ship inside the drydock.
Found a total loss, she was made boyant, amputating her bow, thereby freeing the dock, and was partially scrapped by the German and the Italian and bombed several times by the Allied aircraft. The ship was refloated in 1945, and in a very decrepite state, stricken in 1955. Her remains (not more than some 15,000 tonnes...) were sold for final demolition three years later[74].
Media related to [//commons.wikimedia.org/wiki/Category:Dunkerque_class_battleships Dunkerque class battleships] at Wikimedia Commons
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