Why was Alexander the Great’s Companion cavalry important?

The Companion cavalry (hetairoi) was arguably the finest equestrian unit in the ancient world and served as the decisive striking force in Alexander the Great’s military campaigns.1

Their importance was defined by several key factors:

• Tactical Superiority: The Companions were trained to advance in a wedge or triangular formation, a maneuver specifically designed to penetrate and shatter the enemy's battle line.2
• Decisive Impact: While the phalanx provided a formidable, steady core of heavy infantry, the Companion cavalry acted as the primary offensive weapon. Alexander frequently led them personally to exploit gaps in the enemy's formation, as famously demonstrated at the Battle of Gaugamela, where their charge into the Persian center forced the flight of Darius III.1
• Balanced Warfare: Their effectiveness was enhanced by Alexander’s mastery of combined arms. By coordinating the cavalry with light infantry and archers, he ensured the Companions could strike effectively without being enveloped or hindered by enemy defenses.1

Equipped with breastplates, helmets, and shorter spears, they provided the mobility and shock power necessary to secure victory in pitched battles across the Achaemenian Empire.12