The Sacred Band of Carthage is the name used by Greek historians to refer to an infantry unit of Carthaginian foot citizens that served in Carthaginian armies during the fourth century BC. The presence of Carthaginian citizens fighting as infantry in these armies is unusual as Carthaginian citizens usually only served as officers or cavalry in the Carthaginian armed forces and the bulk of Carthaginian armies were usually made up of mercenaries, infantry from allied communities (who might be Punic colonists) and subject levies.
Trained from an early age to be tough phalanx spearmen, these men were from wealthy Carthaginian families, and as such had extremely good equipment. They were trained from birth to be great warriors and they were able to afford high quality armor and weapons. They fought as a traditional phalanx organized in the Hellenic style.
The "Sacred Band" consisted of a small heavy infantry unit of 2000-3000 men, who were "inferior to none among them as to birth, wealth, or reputation" and distinguished by "the splendour of their arms, and the slowness and order of their march".
At the Battle of the Krimissus in Sicily in 341 BC, the "Sacred Band" fought as a well organized phalanx[1]. It was destroyed utterly. Two thousand citizen troops (perhaps a similar unit), are recorded as being in Sicily in 311 BC, the last time that citizens troops are recorded as being overseas. By 310 BC, the Sacred Band appears to have been reformed, only to be destroyed in battle against Agathocles at Tunis.
After its destruction in 310 BC, the "Sacred Band" disappears from historical record. When Carthaginian citizen infantry turn up in the historical sources during later wars, their numbers are significantly higher implying a levy of all available citizens due to crisis. Larger citizen forces turned out at the Battle of Bagradas during the First Punic War, the Mercenary War, and the Third Punic War, but the "Sacred Band" is not mentioned in any of the surviving accounts we have of these wars.
In the 2004 PC game Rome: Total War, the Sacred Band of Carthage is depicted as a unit of cavalry as well as a hoplite unit.