History of the Peloponnesian War

But the moment they began to give way, the lightarmed troops, now emboldened, fell upon them with a louder outcry than ever. Those of the Lacedaemonians who were intercepted in their retreat were slain, but the majority of them escaped to the fortification, where they ranged themselves with the garrison there, resolved to defend it at every point where it was assailable.

The Athenians followed, but the position was so strong that they could not outflank and surround the defenders. They, therefore, tried to dislodge them by a frontal attack.