The military of Carthage was one of the largest military forces in the ancient world. Although Carthage's navy was always its main military force, the army acquired a key role in the spread of Carthaginian power over the native peoples of northern Africa and southern Iberian Peninsula from the 6th century BC and the 3rd century BC. Carthage's military also allowed it to expand into Sardinia and the Balearic Islands. This expansion transformed the military from a body of citizen-soldiers into a multinational force composed of a combination of allies, citizens and foreign mercenary units.