Hellenistic- "International"period of Greek history, when Greece ruled most of the Mediterranean and southwestern Asia. During and after the rule of Alexander the Great, happened by 300 B.C. Greeks culture was the most popular but the people they conquered weren't forced to change their ways.
Macedonia Map:

Athens lost the Peloponnesian War for many reasons, such as disease. The plague struct Athens hard and nearly wiped out 1/3 of the entire population and even killed their leader. The city couldn't focus on the war when they were struggling to stay alive. The Black Plague killed the leader who thought of going to war with Sparta, leaving the Athenians clueless as to what to do. People could not decide on a leader and Athens never returned to the peaceful place it was before Pericles had passed. Also, Athens fleet of naval ships was being destroyed. By 413 B.C. Athens had lost 2/3 of the ships again Syracuse, Sparta's allies. Spartans became allies with the Persians and built more ships to overcome the power of Athens. With Sparta winning the war and Athens losing many needed ships to transport food and other supplies to survive, Athens lost. The Athenians began starving and were forced to surrender to Sparta.

In 359 B.C. King Phillip II took the throne over Macedonia. He wanted to gain control of all the city-states and bring together a strong force to invade the Persia Empire and take over that land. He made several plans to take over Greece and had secret agents living in the city states to make sure the people didn't rebel against him.