ORDER OF BATTLE // -217 BCE
Battle of the Trebia
Estimated force strength by side, with confidence labels per surviving record.
Forces engaged
2 sides catalogued · combined 80,000 estimated
Carthage
40,000
Medium-confidence figure
Rome
40,000
Medium-confidence figure
Battle context
The Battle of the Trebia was the first major engagement of the Second Punic War, fought on the flood plain of the west bank of the lower Trebia River near Placentia. With each side fielding approximately 40,000 men, the battle ended in a heavy Roman defeat, with Roman casualties reaching 20,000. The outcome demonstrated early in the conflict that Hannibal's army — superior in cavalry to the Roman force under Sempronius Longus — could inflict decisive losses on a Roman army in open battle on Italian soil. As the opening major battle of the war, the Trebia established Hannibal's capacity to operate aggressively in northern Italy and set the conditions for subsequent Carthaginian advances deeper into the peninsula.
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