The Battle of Perachora occurred early in 360 BCE, as a result of a renewed Athenian offensive against the invading Corinthian and Allied armies. Helmetrus, the First General of Athens, moved half of his full force against the Northern Peloponnesian army, while sending 2,000 elite soldiers to support his engagement.
The Athenian attacked King Atimorachus of Corinth (Peloponnesian League King) near a small moutainous region, North of the Isthmus of Corinth. Helmetrus openly attacked Atimorachus with less men in a standard battle, but was able to rally his forces in several key positions that gave him the upper hand. When the battle seemed to have reached a stalemate late in the evening, Helmetrus ordered the hidden Third Army to ambush Atimorachus from the forest behind. The result of the motion was a massive Corinthian rout, though Atimoarchus was able to retreat in good order after the initial rout.
Directly following the battle, Atimorchus was forced to retreat his army South and merge with the Messinan King in an effort to outnumber Helmetrus's forces. His effort was in vain, as the Athenian army was able to defeat the allies for a second time later in the year.
Historians know very little of the Battle of Perachora, excluding a very broad overview (as was presented here), by a unknown Athenian general who was present at the engagment.