The Corinthian invasion of the Isthmus of Corinth in 361 BCE initiated a war between Athens and the Peloponnesian League. The Corinthian navy was able to shuttle troops, supplies and necessities for the army from the Argolikos Koilpos, a body of water east of Corinthian territory.
Due to the fact that the Corinthians had long been planning a invasion, the action was incredibly successful as the allied armies were very mobile, covering three times the distance of a standard Athenian army. Because most of the Athenian forces were quelling rebellions in the Aegean, Timotheus sent half of the Navy to defeat the Allied invasion, which relied heavy on naval capabilities. The Corinthians, as part of their battle plan, had positioned themselves near a defensive collection of islands where they could both fight and shuttle supplies. When the Athenian Navy arrived, they were caught between a division of Corinthian war ships and the rocks. The Athenian Navy, unable to maneuver between the rocks, were then surprise attacked by the main Corinthian fleet that encircled the Athenian Navy. The result was a disastrous Athenian defeat, and the eventual surrender of half the Athenian Navy.
With the waters cleared, Corinth was left with a passage to move its allies armies in. Thousands of allied troops marched into the Isthmus and near the border of Attica.