Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
Battle on the Trebia
Scipio had thus solved his difficult task completely and brilliantly. The Roman army, now close on 40,000 strong, and though not a match for its antagonist in cavalry, at least equal in infantry, had simply to remain in its existing position, in order to compel the enemy either to attempt in the winter season the passage of the river and an attack upon the camp, or to suspend his advance and to test the fickle temper of the Gauls by the burden of winter quarters.
Clear, however, as this was, it was no less clear that it was now December, and that under the course proposed the victory might perhaps be gained by Rome, but would not be gained by the consul Tiberius Sempronius, who held the sole command in consequence of Scipio's wound, and whose year of office expired in a few months. Hannibal knew the man, and neglected no means of alluring him to fight. The Celtic villages that had remained faithful to the Romans were cruelly laid waste, and, when this brought on a conflict between the cavalry, Hannibal allowed his opponents to boast of the victory.
Soon thereafter on a raw rainy day a general engagement came on, unlocked for by the Romans. From the earliest hour of the morning the Roman light troops had been skirmishing with the light cavalry of the enemy; the latter slowly retreated, and the Romans eagerly pursued it through the deeply swollen Trebia to follow up the advantage which they had gained. Suddenly the cavalry halted; the Roman vanguard found itself face to face with the army of Hannibal drawn up for battle on a field chosen by himself; it was lost, unless the main body should cross the stream with all speed to its support.
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Reference address : https://www.ellopos.net/elpenor/rome/3-05-war-hannibal-cannae.asp?pg=7