Athens's parallel rise as a significant power in Greece led to friction between herself with Sparta and two large-scale conflicts (the First and Second Peloponnesian Wars), which devastated Greece. Sparta suffered several defeats during these wars, including, for the first time, the surrender of an entire Spartan unit at Sphacteria in 425 BC. Still, it ultimately emerged victorious, primarily through the aid it received from the Persians. Under its admiral Lysander, the Persian-funded Peloponnesian fleet captured the Athenian alliance cities, and a decisive naval victory at Aegospotami forced Athens to capitulate. The Athenian defeat established Sparta and its military forces in a dominant position in Greece.