Thierry of Alsace (Dietrich) (c. 1099 – January 17, 1168), in Flanders known as Diederik van den Elzas, was count of Flanders from 1128 to 1168. He was the youngest son of Duke Thierry II of Lorraine and Gertrude of Flanders (daughter of Robert I of Flanders). With a record of four campaigns in the Levant and Africa (including participation in the Second Crusade, the failed 1157–1158 siege of the Syrian city Shaizar, and the 1164 invasion of Egypt), he had a rare and distinguished record of commitment to crusading.
After the murder of his cousin Charles the Good in 1127, Thierry claimed the county of Flanders as grandson of Robert I, but William Clito became count instead with the support of King Louis VI of France. William's politics and attitude towards the autonomy of Flanders made him unpopular, and by the end of the year Bruges, Ghent, Lille, and Saint-Omer recognized Thierry as a rival count. Thierry's supporters came from the Imperial faction of Flanders, and upon his arrival he engaged in battle against William.
Louis VI had Raymond of Martigné, the Archbishop of Reims, excommunicate him, and Louis himself then besieged Lille, but was forced to retire when Henry I of England, William's uncle, transferred his support to Thierry. However, Thierry was defeated at Tielt and Oostkamp and fled to Brugge. He was forced to flee Brugge as well, and went to Aalst, where he was soon under siege from William, Godfrey I of Leuven, and Louis VI. The city was about to be captured when William was found dead on July 27, 1128, leaving Thierry as the only claimant to the county.
Thierry set up his government in Ghent and was recognized by all the Flemish cities as well as King Henry, who had his Flemish lords in England swear fealty to him. Thierry himself swore homage to Louis VI after 1132, in order to gain the French king's support against Baldwin IV, Count of Hainaut, who had advanced his own claim on Flanders.
In 1132 his wife, Suanhilde, died, leaving only a daughter. In 1139 then went on pilgrimage to the crusader Kingdom of Jerusalem, and married Sibylla of Anjou, daughter of King Fulk of Jerusalem and widow of William Clito; a very prestigious marriage.
This was the first of Thierry's four pilgrimages to the Holy Land. While there he also led a victorious expedition against Caesarea Phillippi, and fought alongside his father-in-law in an invasion of Gilead. He soon returned to Flanders to put down a revolt in the Duchy of Lower Lotharingia, ruled at the time by Godfrey III of Leuven.
Thierry went on crusade a second time in 1147 during the Second Crusade. He led the crossing of the Maeander River in Anatolia and fought at the Battla of Attalya in 1148, and after arriving in the crusader Kingdom he participated in the Council of Acre, where the ill-fated decision to attack Damascus was made.
He participated in the Siege of Damascus, led by his wife's half-brother Baldwin III of Jerusalem, and with the support of Baldwin, Louis VII of France, and Conrad III of Germany, he lay claim to Damascus; the native crusader barons preferred one of their own nobles, Guy Brisebarre, lord of Beirut, but in any case the siege was a failure and all parties returned home.
During his absence, Baldwin IV of Hainaut invaded Flanders and pillaged Artois; Sibylla reacted strongly and had Hainaut pillaged in response. The Archbishop of Reims intervened and a treaty was signed. When Thierry returned in 1150, he took vengeance on Baldwin IV at Bouchain, with the aid of Henry I, Count of Namur and Henry II of Leez, Bishop of Liège. In the subsequent peace negotiations, Thierry gave his daughter Marguerite in marriage to Baldwin IV's son, the future Baldwin V, Count of Hainaut.
In 1156 Thierry had his eldest son married to Elizabeth of Vermandois, daughter and heiress of Raoul I of Vermandois. In 1156 he returned to the Holy Land, this time with his wife accompanying him. He participated in Baldwin III's siege of Shaizar, but the fortress remained in Muslim hands when a dispute arose between Thierry and Raynald of Châtillon over who would possess it should it be captured. He returned to Flanders 1159 without Sibylla, who remained behind to become a nun at the convent of St. Lazarus in Bethany. Their son Philip had ruled the county in their absence, and he remained co-count after Thierry's return.
In 1164 Thierry returned once more to the Holy Land. He accompanied King Amalric I, another half-brother of Sibylla, to Antioch and Tripoli. He returned home in 1166, and adopted a date palm as his seal, with a crown of laurels on the reverse.
He died on February 4, 1168, and was buried in the Abbey of Watten, between Saint-Omer and Gravelines. His rule had been moderate and peaceful; the highly developed administration of the county in later centuries first began during these years. There had also been great economic and agricultural development, and new commercial enterprises were established; Flanders' greatest territorial expansion occurred under Thierry.
His first wife, Swanhilde, died in 1132, leaving only one daughter:
Thierry secondly married Sibylla of Anjou, daughter of Fulk V of Anjou and Ermengarde of Maine, and former bride of William Clito. Their children were:
| Preceded by William Clito |
Count of Flanders 1128–1168 |
Succeeded by Philip |