Sparta's getting insecure. Athens doesn't listen to Sparta about this wall and decides to start building it. As Sparta's feeling even more insecure. Athens is starting to create this Delian League, which is really an Athenian empire, even more insecure. And it kind of gets a little bit more intense in 464. So there are some accounts that Sparta, around this time, was already planning to invade Athens, to say, hey, these folks are getting too powerful, let's just put them in their place. But at around that time, in 464, you have a major earthquake.