The document discusses the key events that led to the beginning of the Peloponnesian War between Athens and Sparta in ancient Greece in the 5th century BC. It mentions disputes over the city of Potidaea in 435 BC and Corinth aiding Potidaea, which led to an Athenian embargo on Corinth and angered Sparta. Sparta then convened the Peloponnesian council, moving the two cities closer to war. The document states the war evolved from these string of events and the growing power of Athens alarmed Sparta, making war inevitable.