So as Sparta and Athens are starting to become more and more rivals, Sparta's getting insecure about Athens' influence and their resources and their military power. And we even saw it in the last video. You have an earthquake in Sparta, potentially right around the same time that Sparta was planning an invasion of Athens, leaving the Spartans vulnerable. There's a helot uprising, these Spartan slaves. The Athenians send hoplites to apparently help the Spartans, but the Spartans are suspicious of it and they send them back. And then it culminates with the skirmish you have between Megara and Corinth, which were historically two Spartan allies, but Athens decides to take sides, gets an alliance with Megara. And that's one thing too many for the Spartans, and so they declare war.