The Peloponnesian War lasted 27 years, with a brief truce in the middle. An Athenian General, Thucydides, recorded the war. In Thucydides work, The History of the Peloponnesian War, he puts the cause of the war as "fear of the growth of the power of Athens." Athens at this time was the most powerful of all the city-states, and had the best navy in the world. It was also the richest and had the most influence throughout the world, making the other not so powerful city-states very jealous. Athens managed to hold back the other city-states so they could not progress. Sparta, on the other hand, was very strong with its land army and had many professional soldiers. The Spartans believed the key to success was the traditional training, and they were right for centuries because they never lost a battle, even though their army was small in number. He was born in 495 BCE, into the Alcmaeonids family. He had a very wealthy family and had many rich friends. He commanded some of the Athenian allied fleet. He had a lot of experience because of his traveling and exploring, which helped him immensely. Pericles gained power by way of the law courts. .
The Peloponnesian War did not start overnight. There were many events that lead up to the start of the military force. .
During this time Athens had to keep on fighting so that they could show they had a good military, just like the Spartans. All these alliances became known as the Delian League. By now the Athenian fleet had become by far the largest and most formidable navy in the region. One of the main reasons for this was that the Athenians collected tribute (taxes) from the city-states in the Delian League. This tax was in exchange for the protection the Athenian fleet and army provided.