+72.+ As soon as Tiberius saw the Numidian horse approaching, he immediately sent out his cavalry by itself with orders to engage the enemy, and keep them in play, while he despatched after them six thousand foot armed with javelins, and got the rest of the army in motion, with the idea that their appearance would decide the affair: for his superiority in numbers, and his success in the cavalry skirmish of the day before, had filled him with confidence. But it was now mid-winter and the day was snowy and excessively cold, and men and horses were marching out almost entirely without having tasted food; and accordingly, though the troops were at first in high spirits, yet when they had crossed the Trebia, swollen by the floods which the rain of the previous night had brought down from the high ground above the camp, wading breast deep through the stream, they were in a wretched state from the cold and want of food as the day wore on. While the Carthaginians on the contrary had eaten and drunk in their tents, and got their horses ready, and were all anointing and arming themselves round the fires. Hannibal waited for the right moment to strike, and as soon as he saw that the Romans had crossed the Trebia, throwing out eight thousand spearmen and slingers to cover his advance, he led out his whole army. When he had advanced about eight stades from the camp, he drew up his infantry, consisting of about twenty thousand Iberians, Celts, and Libyans, in one long line, while he divided his cavalry and placed half on each wing, amounting in all to more than ten thousand, counting the Celtic allies; his elephants also he divided between the two wings, where they occupied the front rank. Meanwhile Tiberius had recalled his cavalry because he saw that they could do nothing with the enemy. For the Numidians when attacked retreated without difficulty, scattering in every direction, and then faced about again and charged, which is the peculiar feature of their mode of warfare. But he drew up his infantry in the regular Roman order, consisting of sixteen thousand citizens and twenty thousand allies; for that is the complete number of a Roman army in an important campaign, when the two Consuls are compelled by circumstances to combine forces.[184] He then placed the cavalry on either wing, numbering four thousand, and advanced against the enemy in gallant style, in regular order, and at a deliberate pace. [Sidenote: The Roman cavalry retreat.]