If Alexander had not taken control his empire would not have expanded sicne
his father was nto looking for the end of the earth.
The bulk of fighting was entrusted to the Macedonian army
Most of Alexander's generals were Macedonian.
The Macedonian phalanx was Philip's creation, extended by Alexander. Whereas
the Greeks still fought in their traditional three battle lines, the phalanx
was a flexible unit well drilled and able to take on a variety of formations.
It was usually 16 men on a side, 256 men in each unit, always and exclusively
Macedonian. They were armed with the sarissa, a long spear but at 13 feet
actually shorter than the hasta used by Greek hoplites, which was over 16
feet long. The real strength of the phalanx was its many formations and maneuvers.
While the square was the usual formation, it could form a line or wedge or
other shapes. The soldiers were trained to respond to flag and trumpet signals.
No army in the Western world in the 4th century was its equal. http://history.boisestate.edu/westciv/alexander/04.htm