Alexander's return was not a direct one. While the fleet sailed, Alexander also led part of the army on the coast to explore and collect supplies. In the course of the journey he made some poor decisions, including a difficult march through the desert, which resulted in the deaths of almost a quarter of those who began the journey. Though the blame clearly fell on Alexander's overconfidence, he found suitable scapegoats as usual.

Stopping in Persia, Alexander had quite a bit of housekeeping to do. He removed several satraps, executing those whose crimes–usually conspiracy–had been flagrant. His continued desire to unite Persia and Macedonia resulted in a mass marriage, as he paired up eighty of his leading officers with noble Iranian brides.

Alexander made two important decrees before he left Susa in 324 B.C. First, there was the problem of social distress arising from the many Greek mercenaries wandering Asia, who had been exiled from their native lands, often because of Alexander's policies. Alexander made the risky move of restoring all exiles to their native Greek cities, which would likely alienate the leaders of those cities. Alexander's second great decree was that he was now a god. That this decree was due in part to irrationality is possible; Alexander had achieved a great deal in his conquest, and he apparently decided that human honors did not measure up to his greatness. From a young age he had felt destined for divinity, and his experience in Asia and Egypt likely confirmed his belief that he was above the race of men.

After the death of a close friend, Hephaestion, Alexander entered several days of mourning and then decided to undertake a new campaign–which would be his last. His target was a tribe called the Cossaei, who controlled a mountain area and charged a toll on those who needed to pass to reach Babylon or Susa. The Persian leaders had never been able to clear the Cossaei out, and had simply paid the fee. Alexander decided to subdue the tribe, and, after a forty-day campaign, he had virtually annihilated them.

Alexander continued on to Babylon, where he began preparations for his next campaign. In the city he experienced a number of bad omens, though writers may have exaggerated some of these portents to heighten the drama surrounding Alexander's death. On June 3, 323 B.C., Alexander attended two parties that went early into the morning. Afterward he fell feverishly ill, and was incapacitated until his death on June 13. No heir was named; Alexander had indicated that he expected a funeral contest to take place to determine the strongest successor.

Though Alexander's illness was officially attributed to a fever aggravated by heavy drinking, the possibility that he was poisoned has been raised. The suspects are Aristotle and Antipater, both of whom had reason to fear Alexander's retribution for various disloyalties, and both of whom also disliked his favorable treatment of the Persians. Aristotle possessed the knowledge to make the poison and Antipater the means to administer it. Though the poisoning theory will likely never be proven with certainty, most scholars regard it as a strong possibility.

With Alexander's death came the gradual dismantling of the empire, which had no chance of enduring without his leadership. In his thirty-two years he had assembled one of the greatest military records in history. His brilliance as a tactician demonstrated itself time after time, as he systematically conquered a significant portion of Asia one piece at a time. Alexander was particularly effective in adapting to enemy tactics, and he always knew how to exploit a weakness. Moreover, his leadership ability is not to be underestimated. He knew how to choose the right governors and how to keep them in line; he knew when to compromise and when to be obstinate. Alexander may not have enjoyed the love of his subjects–particularly in Greece–but he successfully ruled them by invoking the appropriate balance of fear and respect. Though he was ruthless with potential conspirators, he also had good reason to believe that his life was constantly in danger, as countless previous rulers had lost their lives due to carelessness.

The ultimate extent of Alexander's success remains disputable. Although he has been portrayed as a visionary, he seems to have had little underlying motivation for his expeditions beyond a desire for conquest. Moreover, although he has been praised for uniting the Persians and Greeks, his success may have been overestimated. After his death, the two peoples did not live in the kind of harmony Alexander had envisioned.

Despite these shortcomings, Alexander's influence on the development of the world is not to be doubted. He founded an estimated seventy cities and made room for the spread of Greek culture in the East. More importantly, he opened up increasing possibilities for trade and social communication between East and West. Ultimately, the building of the Roman Empire can be traced to seeds that Alexander planted. While he may have viewed himself as above the human race, there is no doubt that few men have changed the course of human history to a comparable extent.