1. The Trebia December [?], 218 BC
Strategic Context
In 218 BC, Hannibal Barca negates Roman control of the seas by leading the Carthaginians through Spain to attack Roman territory, igniting the Second Punic War. Hannibal defeats one Roman army under Scipio Africanus at the Ticinus River while another under Tiberius Sempronius departs Sicily to combine forces. The combined Roman army camps opposite the Carthaginian army across the Trebia River. Hannibal sends his cavalry to provoke the impulsive Sempronius and succeeds: the Romans wade across the frigid Trebia River to attack while the Carthaginians warm by the fire.
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Stakes
+ A Carthaginian victory would shake Roman confidence and summon disgruntled Roman allies to the Carthaginian cause.
+ A Roman victory would deny the Carthaginians a secure base in Italy.
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By Jonathan Webb, 2009

2. The Trebia, 218 BC Strength Carthaginians Well Romans Severely cold
Hannibal
Tiberius Sempronius Longus
20,000 infantry
36,000 infantry
10,000 cavalry
4,000 cavalry
2 war elephants
By Jonathan Webb, 2009

3. Mediterranean c. 218 BC

4. The battlefield consists of a flat, snowy plain surrounded by rough terrain to the west and north in the form of rugged hills. The Po River to the north also restricts movement in that direction, with the much shallower, narrower Trebia river running north-south, bisecting the battlefield. The weather is cold and snowy however, making even the chest-deep Trebia River a significant obstacle.
500m
1 km
Carthaginians
(Hannibal)
Po River
Trebia River
Romans
(Sempronius)

5. (Tiberius Sempronius Longus)
Hannibal transfers his elephants to his left and attacks; the Roman cavalry are defeated and now the Gallic allied infantry guarding the Roman flanks come under attack. Mago emerges from hiding to sweep behind the Roman rear to complete the encirclement. Meanwhile, the Roman infantry desperately batter the opposing Carthaginian infantry.
Sempronius sends his infantry forward in typical Roman fashion, steady and in good order. They dismiss the Carthaginian elephants but are unable to decisively push the outnumbered Carthaginian infantry backwards. Meanwhile, Hannibal counterattacks the Roman cavalry with his own and succeeds in bending back the Roman line by the flanks.
Hannibal becomes preoccupied with reducing the trapped Roman pocket by assaulting its flanks. Roman infantry in the center are thus able to slice through the Carthaginian infantry line and escape along with Sempronius himself. The remaining Roman units are annihilated fighting or drowned trying to escape.
Sempronius deploys his veteran legionnaire infantry in the center, flanked by his Gallic allied infantry and then his cavalry. Hannibal deploys his infantry in a thin line in the center, flanked by his few elephants and then his cavalry. He detaches a cavalry force under Mago to remain unseen in a ravine near the Roman left and to only reveal his position at the most opportune time.
500m
1 km
Carthaginians
(Hannibal)
Hannibal
Carthaginians Romans
Infantry Infantry
Cavalry Cavalry
War elephant
Camp Camp
Mago
Carthaginians
(Hannibal Barca)
20,000 infantry
10,000 cavalry
2 war elephants
Romans
(Tiberius Sempronius Longus)
36,000 infantry
4,000 cavalry
Symbol guide
Romans
(Sempronius)

6. The Trebia, 218 BC Casualties & Aftermath
Carthaginians:
Romans:
5,000 or
16%
30,000 or
75%
Both sides quietly retreated to winter quarters to rest, Sempronius only telling the Roman Senate that he had entered battle but did not achieve victory due to poor weather. By spring the next year, Sempronius and Scipio were replaced as consuls. Their successors fared no better at the Battle of Lake Trasimene in 217 BC as Hannibal continued to ravage each Roman force sent against him. Only in 202 BC did Hannibal meet his match, being decisively defeated by Scipio Africanus (the Younger) at the Battle of Zama.
By Jonathan Webb, 2009

7. The Art of Battle: Animated Battle Maps
By Jonathan Webb, 2009