Book VIII, 13-20.

Background:

In 260, we find Pyrrhos and his army of runaway Italians in Asia Minor. He was there either a mercenary general or simply as a friend of Ptolemaios Philadelphos, king of Ptolemaic Egypt.
Whether he was welcomed at the court as an long time ally as the legitimate king of Epeiros or just hired as a mercenary, we may never know. But it is certain that Ptolemaic Egypt needed all the help they could get at this point.
The empire of that other successor, Seleukos, was laying waste to much of the countryside of Asia Minor. All Ptolemaic strongholds there were under siege too. Pyrrhos was sent to one those important towns under siege, the city of Tarsos.

The text:

[…]
The Syrians had set up their camp between the city walls and the river Kydnos. Scouts soon found a fordable place some distance from the main road. Pyrrhos knew he had to wait though, since his army numbered only 2000 foot and 500 horse.
The horses he had been given from the stables of Ptolemaios himself, since Pyrrhos himself had not brought any on the ships.
[…]
The small army made manoeuvring easier for Pyrrhos and he sneaked closer and closer to the river without being noticed by the Syrian commander. Of the infantry he set 1500 men near the main road to cross the river at the bridge. he horse, and the rest of the infantry he took with him to the shallow spot of the river.
[…]
At this sign, Zenodotos Euergetes, governor of Tarsos sallied out. The Syrian commander Omanes Bethalagas reacted forming a battle line as close a he could towards the city. He left 5000 men to guard the bridge over the Kydnos.
[…]
The split, panicked and disorganised Syrian rearguard was soon beaten, both at the shallows and at the bridge. Pyrrhos’ soldiers then marched upon the engaged and unsuspecting Syrians.
[…]