The ancient Greeks had an extraordinary level of cultural achievement in almost every field of human endeavor. Their culture gave birth to art, drama, philosophy, science and mathematics that still have a tremendous impact on our world today.
However, their civilization eventually fell into decline, which led to its collapse. There are several reasons for this decline:
The population decline occurred because people were leaving their homes for better opportunities elsewhere or because they were killed due to war or disease.
Political collapse: In addition to these two causes, Ancient Greece also fell because of political collapse. The Athenian democracy became increasingly corrupt over the centuries leading up to its fall, which contributed to its downfall.
Decline of trade: Trade declined significantly during this period as well; this was partly due to the fact that other nations were starting to dominate trade routes between Europe and Asia Minor (Turkey).
Military weakness: The Greek city-states were no longer united under one ruler like Alexander the Great had been; instead they were constantly fighting each other or being invaded by other peoples such as the Gauls (French). This made them less effective militarily than they had been when they were united under Alexander’s rule or that of earlier rulers like Philip II (father of Alexander).