Philip's military innovations created the fighting power that Alexander inherited, making it a force to be reckoned with. Philip introduced the 12 cubit (6 meter) sarissa, a wooden pike with metal tip, for use by his infantry in the phalanx. The sarissa, when held upright by the rear rows of the phalanx (there were usually eight rows), helped hide maneuvers behind the phalanx from the view of the enemy. When held horizontal by the front rows of the phalanx, it was a rather brutal weapon. People could be run through from 20 feet away, giving quite an advantage to the phalanx in hand-to-hand combat.
Philip made the military a way of life for many Macedonian men. In the past, soldiering had only been a part-time job, something the men would do during the off peak times of farming. When the fighting season ended at the start of the harvest, the men would return to the farms. Philip made the military an occupation that paid well enough that the soldiers could afford to do it year-round.
By making the military a full-time occupation, Philip was able to drill his men regularly, building unity and cohesion within the army. Alexander fought with the finest military machine that Asia or Greece had ever seen, primarily because of the amount of time and effort spent on maneuvers.
In addition to the basic phalanx, Philip and Alexander used light auxiliaries, archers, a siege train, and a cavalry. With all of these working well together, both Philip and Alexander rarely, if ever, lost any battle.