Alexander's greatest achievement was uniting Greece. He brought together the Greek city-states, which had been constantly at war with each other, and created a unified Greek kingdom. This allowed the Greeks to become a major power in the Mediterranean world and to spread their culture and civilization throughout the region.
Conquering the Persian Empire
Alexander's other great achievement was conquering the Persian Empire. The Persian Empire was the largest empire in the world at the time, and Alexander defeated the Persians in a series of battles. This allowed Alexander to create a vast empire that stretched from Greece to India.
Creating a Hellenistic Civilization
Alexander's conquests also led to the creation of a Hellenistic civilization. This was a blend of Greek and Persian culture, and it spread throughout the Mediterranean world and the Middle East. Hellenistic civilization had a profound impact on the development of Western civilization.