Indian campaign of Alexander the Great

The Indian campaign of Alexander the Great began in 327 BC and lasted until 325 BC. After conquering the Achaemenid Persian Empire, the Macedonian army undertook an expedition into the Indus Valley of Northwestern Indian subcontinent. Within two years, Alexander expanded the Macedonian Empire, a kingdom closely linked to the broader Greek world, to include Gandhara and the Indus Valley of Punjab and Sindh (now in India and Pakistan), surpassing the earlier frontiers established by the Persian Achaemenid conquest.

Source: Wikipedia — Indian campaign of Alexander the Great (CC BY-SA 4.0)