Who was Alexander's main enemy during his conquests?

The main enemy of Alexander the Great during his conquests was Darius III, the king of the Persian Empire. Alexander's military campaigns primarily focused on the conquest of Persia, which was the dominant power in the region at the time. Darius III led the Persian forces against Alexander in several significant battles, including the Battle of Granicus, the Battle of Issus, and the Battle of Gaugamela.

These confrontations were pivotal in establishing Alexander's reputation as one of history's great military tacticians and conquerors. Darius's inability to effectively unite and lead his forces against Alexander allowed the latter to achieve remarkable victories and expand his empire across much of the known world.

The other individuals listed do not represent enemies during Alexander's conquests. Philip II was Alexander's father, who unified Macedonia and set the stage for Alexander's future achievements. Aristotle was Alexander's tutor and a significant influence on his education, particularly in philosophy and science. Hannibal was a military commander from Carthage who lived around 200 years later and is best known for his conflicts with Rome during the Second Punic War. Thus, Darius III stands out as the primary adversary against whom Alexander fought during his campaign to conquer Persia.