But what was it that made Alexander such a successful commander?
First let's draw a comparison to another great general, Napoleon Bonaparte. Napoleon is credited with utilizing the idea of separate, self-sufficient army formations. Before Napoleon, every nation had an army with a general. This army had one supply train, one chain of command, one army camp when not moving, and always fought more or less together.
Yet, Napoleon's greatest strengths might have been his charisma, political leadership, and diplomat skills. His military skills, as great as they were, lacked the vision and planning of leaders such as Genghis Khan and Alexander the Great. For example, I doubt that either one of those military leaders would have made the mistakes Napoleon made in invading Russia, where his army started off with over 600,000 men and only 100,000 returned. Napoleon fought in over 60 battles, and lost 7 of those conflicts.
Alexander the Great fought military campaigns for over fifteen years and never lost a battle.