The "Thirty Years' Peace" was a treaty established in 421 BCE between the city-states of Athens and Sparta, marking a temporary cessation of hostilities in the Peloponnesian War. This agreement aimed to create stability in Greece after years of conflict, allowing both sides to focus on internal affairs and economic recovery. The peace lasted until 413 BCE, when tensions resurfaced, leading to renewed warfare. The treaty included provisions for mutual respect of territories and alliances, but underlying rivalries and ambitions ultimately undermined its effectiveness, contributing to the eventual escalation of the Peloponnesian War.