Peace of Nicias
In 415, Athens and Sparta had been formally at peace since 421, when the Peace of Nicias had brought the Archidamian War to a close. The terms of that peace, however, had never been fulfilled; Sparta had never surrendered Amphipolis to Athens, as required by the treaty, and in return the Athenians had held Pylos. More recently, Athenian and Spartan troops had fought at the Battle of Mantinea in 418, with Athens supporting Argos, Mantinea, and other Peloponnesian cities in an attempt to establish a stable anti-Spartan alliance in the Peloponnese. That attempt, largely orchestrated by the Athenian nobleman Alcibiades, would have destroyed Sparta's control over the Peloponnesian League had it succeeded. Alcibiades rebounded politically from this defeat, and was elected as a general in the spring of 417. Control of Athens' foreign policy remained divided between a "peace party" (or pro-Spartan party) led by Nicias, and a "war party" led by Alcibiades.