Alexander the Great brought massive change to the ancient world. When he became king of Macedonia, he set out on a mission to conquer the known world. As Greece was considered to be home to the most educated and philosophical minds, it only leads to the next possible conclusion - to rule the known world while expanding and extending culture, education and strength.
One easy answer to how Alexander managed to change the world is that - he NEVER lost a battle unless you count the engagement against King Porus as a defeat, which historians still debate over. But young Alexander the Great set out to conquer the known world, expanding the empire of Macedonia to impressive heights.
His goal was to bring Greek culture to more places. However, he also changed warfare throughout the known world. He learned tactics from each military force he encountered, and through his acquisition of that country, his army left their tactics behind as well.
His command over his armies was established through loyalty and example. He went through hardships with them, as well as listening to what his generals shared. In addition, battle tactics were something that Alexander excelled at. He embraced and advanced the use of cavalry in the field, which could turn the course of a battle. He could employ them in large or small units. In the heat of battle, different tactics must sometimes be used.
Alexander was not afraid to change the battlefield by deploying troops or moving them to more effective positions. By not using long-held tactics, which many of his enemies held to, the layout of the battle could quickly shift in another direction. He also used the Greek phalanx to great distinction, which allowed the Macedonian army to gain the upper hand on their enemies more than once.
Once a phalanx was formed, they were not easily broken. A phalanx is a box created by soldiers locking their shields together to protect their bodies, on all sides and overhead, but still allowing for the use of spears. This effective battlefield tactic helped to bring many kingdoms under the control of Alexander the Great.