Peloponnesian War (by Tony Xiao):

After the Greco-Persian wars, Athens and Sparta, two of the most powerful city-states started forming their own leagues, Athens creating the Delian League, and Sparta creating the Peloponnesian League. In the end, Sparta, a highly trained military state and the Peloponnesian League won with help from Persia, though the process weakened Greece greatly. This war occurred from around (431-404 B.C.).

Peloponnesian War picture.jpg
In the end, Mighty Sparta managed to breach Athens' almost unbreakable defenses with help from a powerful Persian navy.

Causes:

After the second war against Persia, Athens decided to create a league to protect Greece where cities would pay money to the all powerful Athens to protect them. Meanwhile, the cities like Sparta that were afraid of the new form of government, Democracy that Athens was starting, formed the Peloponnesian League. But in time, Athens became a little disproportionate, and started misusing power. The cities that wanted to leave the league were stopped or punished, the money that was supposed to be for protection was used for Athens’ interest(like the Parthenon Temple). This greatly upset cities not only Peloponnesian League and some cities in the Delian League. Sparta decided that this was a great disrespect and so the war began.

Important Events:

(431-425 B.C.)-Sparta sends a huge army of trained armored hoplites (which are slaves that Sparta captured in wars and are meant to farm for Sparta) to lead Athenians out of their city walls. But despite all the chaos, no Athenian emerged, and the effort was wasted. But it turned out the wheel of fortune was pointed toward them still. Soon, a plague broke out in Athens. Tons of people died, including Pericles.(425 B.C.)- Athens greatest success was the occupation of Pylos off the coast of the Peloponnesus, where Spartan defenders were taken hostage and the way was made clear for Helot runaways.(421 B.C.)- The frequent failure of Sparta to destroy Athens in the first decade of the war led to a brief peace.(418 B.C.)-Soon, the Athenians intervened in the Peloponnesus and attacked neutral states in the Aegean.(415-413 B.C.)-Nearly 40,000 Athenian perished 1,000 miles away from Athens.
(404 B.C.)-With a massive navy that Persia lent and a menacing army of Sparta itself, Sparta launches a heavy attack which catches victory.
Peloponnesian War picture #2.jpg
A history drawing of Sparta vs Athens.

After this cruel war finished, Greece was left weaker than before, which lead to the triumph of Great Macedonia from later on.

Works Cited
Andrews, Evan. “8 Reasons It Wasn’t Easy Being Spartan.” H History. H History, 5 Mar. 2013. Web. 10 Dec. 2014. <http://www.history.com/news/history-lists/8-reasons-it-wasnt-easy-being-spartan>.
Andrews, Evan. “8 Reasons It Wasn’t Easy Being Spartan.” H History. H History, 5 Mar. 2013. Web Image. 10 Dec. 2014. <http://www.history.com/news/history-lists/8-reasons-it-wasnt-easy-being-spartan>.
“Peloponnesian War.” H History. H History, 2009. Web. 11 Dec. 2014. <http://www.history.com/topics/ancient-history/peloponnesian-war>.
NF, Mihajlo. “spartans.” Fanpop. Fanpop, 2013. Web Image. 11 Dec. 2014
<http://www.fanpop.com/clubs/300/images/2507463/title/spartans-wallpaper> .