1 Alexander took the long route
While marching towards Babylon, Alexander took the longer northern route instead of the shorter southeastern one. This move took the Persians by surprise who expected Alexander to come through the short road.
2 The Persians didn't break the supply lines
The Persians failed to disrupt the supply lines of the Macedonian. One reason for that was the surprise move Alexander did when he took the Northern route. See why Alexander was called the great.
3 Many Persian men weren't real soliders
While the whole of Alexander's army was formed of trained soldiers, the Persian army had a variety of people ranging from trained soldiers to mercenaries.
4 Alexander used an innovative attack strategy
Alexander used an innovative attack strategy that was never used before. He ordered his army to march forward with its left and right wings tilted 45 degrees. This strange formation confused the Persian army and forced the cavalry to attack the wings.
5 Alexander confused the Persian army
Instead of attacking directly with his cavalry, Alexander rode parallel to the Persian army in order to let some follow him and create a gap in the center that can allow him to kill the Persian leader, Darius.
6 The Macedonian phalanx was powerful
The Macedonian phalanx was a very powerful and fierce unit with very strong battle experience. This allowed them to advance easily through the Persian lines.
7 Alexander's army trapped the war chariots
Alexander developed an innovative technique that allowed his men to trap a war chariot, thus making it ineffective. As the war chariots were trapped, the Persian army lost one of its strongest units.
8 The Macedonian phalanx had long weapons
The Macedonian phalanx had very long spears, around 5 meters. This made them superior to many short ranged units who could hardly harm them from a distance.
9 A gap was formed in the Persian army
Alexander's maneuvers worked and a gap was created in the middle of the Persian army. The Persian army lost its balance as the Macedonian cavalry led by Alexander marched through the gap.
10 Darius escaped
The Persian leader, Darius, escaped, thus the army was broken down easily and the Macedonians won.