Alexander paused his campaign to pay off his men and allow some of his troops to return to Greece. He then arranged for thousands of his Greek and Macedonian officers to marry Persian noblewomen in an effort to formally and permanently fuse together the Greek and Persian civilizations. His goal was not to devastate the empire, but to become the next “Great King” to whom all other leaders had to defer. He maintained the Persian bureaucracy (such as the organization of the Satrapies) and enlisted thousands of Persian soldiers who joined his campaign as his armies moved even farther east. He also made a show of treating Darius's family with respect and honor; he wanted to win the Persians over rather than humiliate them.
Alexander declared that the ancient city of Babylon would be his new capital. Even though he now ruled over the largest empire in the world, however, he was unsatisfied, and he set off to conquer lands his new Persian subjects told him about beyond the borders of the empire.
Alexander headed east again with his armies, defeating the tribesmen of present-day Afghanistan and then fighting a huge battle against an Indian king in the northern Indus River Valley in 327 BCE. He pressed on into India for several months, following the Indus south, but finally his loyal but exhausted troops refused to go on. Alexander had heard of Indian kingdoms even farther east (i.e. toward the Ganges River Valley, completely unknown to the Greeks before this point) and, being Alexander, he wanted to conquer them too. His men, however, were both weary and rich beyond their wildest dreams. Few of them could see the point of further conquests and wanted instead to return home and enjoy their hard-won loot. Some of his followers were now over 65 years old, having fought for Philip II and then Alexander in turn, and they concluded that it was high time to go home.
Alexander consulted an oracle that confirmed that disaster would strike if he crossed the next river, so after sulking in his tent for a week, he finally relented. To avoid the appearance of a retreat, however, he insisted that his armies fight their way down the Indus river valley and then across the southern part of the former Persian empire on their way back to Mesopotamia. Unfortunately, Alexander made a major tactical error when he reached the Indian Ocean, splitting his forces into a fleet and a land force that would travel west separately. The fleet survived unscathed, but the army had to cross the brutally difficult Makran desert (in the southern part of present-day Pakistan and Iran), which cost Alexander’s forces more lives than had the entire Indian campaign.
The return journey was arduous, and it took years to get back to the heartland of Persia. In 323 BCE, his armies finally arrived in Babylon. Alexander was exhausted and plagued by injuries from the many battles he had fought, but Macedonian and Greek tradition required him to drink to excess with his generals. Some combination of his injuries, alcohol, and exhaustion finally caught up with him. Supposedly, while he lay on his deathbed, his generals asked who would follow him as Great King and he replied “the strongest,” then died. The results were predictable: decades of fighting as each general tried to take over the huge empire Alexander had forged.
The true legacy of Hellenistic civilization was not Alexander's wars, as remarkable as they were, but their aftermath. During his campaigns, Alexander founded numerous new cities that were to be colonies for his victorious Greek soldiers, all of which were named Alexandria except for one that he named after his horse, Bucephalus. For almost 100 years, Greeks and Macedonians streamed to these colonies, which resulted in a tremendous growth of Greek culture across the entire ancient world. They also came to settle in conquered Persian cities. Everywhere, Greeks became a new elite class, establishing Greek laws and Greek buildings and amenities. At the same time, the Greeks were always a small minority in the lands of the east, a fact that Alexander had certainly recognized. To deal with the situation, not only did he encourage inter-marriage, but he simply took over the Persian system of governance, with its royal road, its regional governors, and its huge and elaborate bureaucracy.