Every preparation having been made, as soon as the moon set, Lagoras and his party came stealthily up to the foot of the cliff with their scaling ladders and concealed themselves under a projecting rock.
At daybreak, as the watch was withdrawing from this spot, and the king, as was his custom, was engaged in sending some troops to the outposts and in marching the main body out to the hippodrome and there drawing them up in battle order, at first no one had any inkling of what was occurring.
But when two ladders were set up and Dionysius was the first to mount the one and Lagoras the other, there was a great excitement and commotion in the army.
It so happened that the assailants could not be seen by those in the town or from the citadel by Achaeus owing to the projecting brow of the rock; but the venturesome and perilous ascent was made in full view of Antiochus' army;
so that either from astonishment and surprise or from apprehension and fear of the result all stood breathless but at the same time overjoyed.
The king, therefore, noticing this excitement in the camp and wishing to divert the attention both of his own forces and of the besieged from his attempt, advanced his army and made an attack on the gate at the other side of the town, known as the Persian gate.
Achaeus, observing from the citadel the unusual movement of the enemy, was for long quite at a loss, being entirely puzzled and unable to understand what was going on.
However, he sent off to meet them at the gate a force which was too late to assist, as they had to descend by a narrow and precipitous path.
Aribazus, the commander of the town, advanced unsuspectingly to the gate which he saw Antiochus was attacking, and making some of his men mount the wall sent the rest out through the gate, with orders to engage the enemy and check his advance.
Walbank Commentary