And that's one thing too many for the Spartans, and so they declare war. And you have what's called the First Peloponnesian War, but that's not the Peloponnesian War. That's the first time that you start having a very open conflict between the Spartans and the Athenians. And these conflicts last for on the order of about 15 years, and they're ended with what's called the Peace of 30 Years. But as we will see, this Peace of 30 Years only lasts about 15 years. And the whole time, tensions continue to arise. The Delian League, or you could call it the Athenian Empire, is getting more and more powerful.