as a phalanx. Slingers were frequently recruited from the Balearic Islands. Roman and Greek sources refer to these foreign fighters derogatively as "mercenaries", but the modern historian Adrian Goldsworthy describes to this as "a gross oversimplification". They served under a variety of arrangements; for example, some were the regular troops of allied cities or kingdoms seconded to Carthage as part of formal treaties. The Carthaginians also employed war elephants; North Africa had indigenous African forest elephants at the time. Background Start of the war The Roman Republic had been aggressively expanding in the southern Italian mainland for a century before the First Punic War. It had conquered peninsular Italy south of the River Arno by 272 BC. By this time Carthage, with its capital in what is now Tunisia, had come to dominate southern Spain, much of the coastal regions of North Africa, the Balearic Islands, Corsica, Sardinia, and the western half of Sicily in a military and commercial empire. In the 3rd century BC Carthage and Rome were the preeminent powers in the western Mediterranean. In 264 BC the two cities went to war over the city of Messana (modern Messina) in the north-eastern tip of Sicily. Much of the war was fought on, or in the waters near, Sicily. Away from the coasts its hilly and rugged terrain made manoeuvring large forces difficult and favoured defensive over offensive operations. Land operations were largely confined to raids, sieges and interdiction. Garrison duty and land blockades were the most common operations for both armies; only two full-scale pitched battles were fought on Sicily during the 23-year-long war; Panormus was one of these. After several Roman successes the war on Sicily reached a stalemate, as the Carthaginians focused on defending well-fortified towns and cities; these were mostly on the coast and could be supplied and reinforced without the Romans being able to use their superior army to interfere. Invasion of Africa From 260 BC the focus of the war shifted to the sea. The Romans won naval victories at Mylae (260 BC) and Sulci (258 BC), and their frustration at the continuing stalemate in Sicily led them to develop a plan to invade the Carthaginian heartland in North Africa and threaten the city of Carthage (close to modern Tunis). After defeating the Carthaginians at the Battle of Cape Ecnomus, possibly the largest naval battle in history by the number of combatants