Essentially a conflict between a land power and a sea power, the Peloponnesian war descended into a grim struggle in which moral standards declined and atrocities were perpetrated on civilian populations. Comparisons can be made between the siege operations of the Spartan and Athenian protagonists and in the developing naval tactics employed where a mixture of attitudes emerged among commanders?some put honor above all else, while others pursued personal ambition. In 431 BC, the threat of war between Sparta and her allies and the Athenian Empire became a reality. For many years Athens enjoyed supremacy at sea while avoiding any land engagements with Spartan led land forces. The setback for the Spartans at Sphakteria at the hands of Demosthenes and Kleon inevitably led to the so-called "Peace of Nikias," despite the major successes in the north of the brilliant Spartan commander Brasidas. Alkibiades persuaded the Athenians to attack Sicily but they were met with an unexpectedly aggressive defence led by the Spartan Gylippos. Monies from the old enemy, Persia, gave Sparta the opportunity to retain highly trained crews which gave Lysander the final victory.