When Ptolemy and his sister after their progress had reached the extremity of his left wing and Antiochus with his horse-guards had reached his extreme right, they gave the signal for battle and brought the elephants first into action.
A few only of Ptolemy's elephants ventured to close with those of the enemy, and now the men in the towers on the back of these beasts made a gallant fight of it, striking with their pikes at close quarters and wounding each other, while the elephants themselves fought still better, putting forth their whole strength and meeting forehead to forehead.
The way in which these animals fight is as follows. With their tusks firmly interlocked they shove with all their might, each trying to force the other to give ground, until the one who proves strongest pushes aside the other's trunk,and then, when he has once made him turn and has him in the flank, he gores him with his tusks as a bull does with his horns.
Most of Ptolemy's elephants, however, declined the combat, as is the habit of African elephants;
for unable to stand the smell and the trumpeting of the Indian elephants, and terrified, I suppose, also by their great size and strength, they at once turn tail and take to flight before they get near them.
This is what happened on the present occasion; and when Ptolemy's elephants were thus thrown into confusion and driven back on their own lines, Ptolemy's guard gave way under the pressure of the animals.
Meanwhile Antiochus and his cavalry riding past the flank of the elephants on the outside attacked Polycrates and the cavalry under his command,
while at the same time on the other side of the elephants the Greek mercenaries next the phalanx fell upon Ptolemy's peltasts and drove them back, their ranks having been already thrown into confusion by the elephants.
Thus the whole of Ptolemy's left wing was hard pressed and in retreat.
Walbank Commentary