The development of the saddle as well as increasingly larger horse breeds led to creation of the Macedonian Companion cavalry developed during the reign of Philip II of Macedon, likely based on the Theban model, as he had spent his youth in the house of Epaminondas as a hostage. This force was later used with great effect by his son, Alexander the Great. In both role and equipment, the Companions was the first cavalry force that was known to represent archetypal heavy cavalry. The Companion cavalry, or "Hetairoi", were the elite arm of the Macedonian army, and have been regarded as the best cavalry in the ancient world.