Panhellenism is a way of thought that originated in ancient Greece

Ancient Greece

Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...

, which recognized that though all city-states were independent of each other, they were all still Greek

Greeks

The Greeks, also known as the Hellenes , are a nation and ethnic group native to Greece, Cyprus and neighboring regions. They also form a significant diaspora, with Greek communities established around the world....

 and should be expected to unite in defense of a common enemy when necessity required it. The word's etymology comes from 'pan' (all) and 'Hellenes' (Greeks). An alternate form of Panhellenism is the idea of a Greek nation state.

Alexander the great , as well as his father Phillip II, were seen as Panhellenic leaders, and allowed an overcrowded Greek population to be able to expand into Asia.

The major advocate of Panhellenism was the Athenian Isocrates

Isocrates

Isocrates , an ancient Greek rhetorician, was one of the ten Attic orators. In his time, he was probably the most influential rhetorician in Greece and made many contributions to rhetoric and education through his teaching and written works....

.