What treaty made peace between Sparta and Athens in 421 BCE?

The Peace of Nicias made a formal peace between Sparta and Athens in 421 BCE.

The agreement was intended to end the Archidamian War, the opening phase of the Peloponnesian War. It was named after Nicias, the prominent Athenian statesman who supported a negotiated settlement.

The treaty planned a fifty-year peace and called for the return of captured places and prisoners. In practice, implementation was incomplete. Several of Sparta’s allies disliked the arrangement, and neither side fully trusted the other.

The peace did not resolve the competition between the two Greek powers. Hostilities soon resumed, and the wider Peloponnesian War continued until Athens finally surrendered to Sparta in 404 BCE.