From Wikipedia

Macedonian Warriors

The Macedonian army or army of Macedon, was the army of the ancient kingdom of Macedonia. It is considered to be among the greatest military forces of the ancient world. It became the formidable force known from history first under the rule of King Philip II of Macedon and then his son, Alexander the Great.

The latest innovations in weapons and tactics, along with unique combination of military elements introduced by Phillip II, came together into the army that won an intercontinental empire. By introducing the military as a full-time occupation, Philip was able to drill his men regularly, ensuring unity and cohesion in his ranks. In a remarkably short time, this led to one of the finest military machines that Asia or Greece had ever seen.

Tactical innovations included the latest tactics applied on the traditional Greek phalanx by men such as Epaminondas of Thebes (who twice defeated the Spartans), as well as coordinated attacks (early combined arms) between the various arms of his army—phalanx, cavalry, missile troops, and (under Alexander III) siege engines. Weapons introduced included the sarissa, a type of counter-weighted (like all Greek spears) long pike, which gave its wielder many advantages, both offensively and defensively.

The new Macedonian army was an amalgamation of different forces. Macedonians and other Greeks (especially Thessalian cavalry) and a wide range of mercenaries from across the Aegean were employed by Phillip. By 338 BC, more than a half of the army for his planned invasion of Persia came from outside the borders of Macedon--from all over the Greek world and the nearby barbarian tribes.