The phalanx proved to be the military success of the ancient Greece, perfected by the warring society of Spartans and copied the world over. By the time of Alexander the Great, the phalanx continued to be the bread-and-butter infantry unit for winning battles and became a large part of the formula of Alexander's successes. Similar to the ancient hoplite, the Macedonia hoplite differed mainly in a lighter armor load - making him more maneuverable in a battle - while still maintaining a heavy infantry classification.
The primary differences between Alexander's hoplite and that of ancient Greece was in the length of the sarissa. Sarissa's were nothing more than thrusting spears but in Alexander's phalanxes, the sarissa - now growing to some 18 feet in length - allowed the phalanx to remain untouchable from forward cavalry attacks. Any charging cavalry would have to face the effects of some hundred forward and angled pointing spears in the immovable approaching or stationary phalanx. Alexander's use of such tactics was on display throughout his known and documented conquests. In addition to the longer sarissa, the Macedonian hoplite also utilized a smaller rounded shield - easier to maneuver while still supplying some form of critical protection from slicing, stabbing and artillery weaponry.
An armored helmet protected the skull and face while a tough cuirass provided limited protection for the chest, stomach area and groin. Feet covering was nothing more than sandals which - considering the climate in the Middle East - was more than appropriate for the phalanx infantry. The Macedonian hoplite's armament was topped off with his sword, which was unsheathed in close-combat once the sarissa's range was no longer an advantage.
As with any plodding ancient formation, the Macedonian hoplite was susceptible to ranged weapons particularly from archers, slingers or javelin-throwing peltasts. Whereas Ancient Greece phalanxes were at their mercy due to their excessive combat weight, Alexander's lightened Macedonian hoplites stood a fighting chance to run down and kill the mobile artillery units. Coupled with his Companion Cavalry, war elephants and Alexander's own ingenuity to adapt to battlefield conditions, the Macedonian phalanx was indeed a pivotal part of his many successes in his short-lived empire.