All the Macedonian heavy cavalry – 1,800 men in all – was in the senior regiment of the army, its riders recruited from among the sons of the noblest Macedonian families. The regiment consisted of eight squadrons (ile), of 200 men each; only the royal one had 400, and these were the crème de la crème. A squadron was divided into four smaller units: tetrarchia, each with 49 men. Squadrons were commanded by an ilearch, and were probably accompanied by a trumpeter.

The figure of 49 was decided very simply: the tetrarch was at the head of the unit, with three men in the first line behind him, five in the second, seven in the third and so on up to the last, which had 13 men. This triangular formation was introduced into the Macedonian army by Philip II. It had the advantage of making possible sudden turns to the left or right, at some 45 degrees, which gave the unit more manouverability than the line formation used by the Persian cavalry. There was no need for the whole unit to turn; each man just turned half-left or half-right, and the left or right side of the triangle became the new front line of the unit, with seven Companions (heteroi), in the first line and six in the second. The men in the first line were spaced, so those in the second line were not hindered in the charge. This gave the tetrarchia a striking front line of 13 men, and 52 for the whole ile. The four tetrarchias in an ile were arranged like the teeth of a saw, one beside the other, so did not present each other with obstacles to straight or diagonal movement. Several iles made up a cavalry brigade (hipparchy) commanded by a hipparch. The execution of their complex manoeuvres in battle conditions required strong discipline and a high level of training.

Each squadron of the Companions was recruited from its county and bore its name, and probably had its distinctive colours too. Equipment and weaponry did not differ much from the Greek, but the helmet was distinctly Macedonian. Later, during campaigns lasting several years, lost equipment was made good in various ways, and the appearance of the men became Hellenic. Alexander himself had his helmet damaged by an axe blow from a Persian rider at the Battle of Granicus, and replaced it with a Boeotian helmet.

In ancient times, lions and leopards lived in Macedonia and are mentioned by Roman sources several centuries later. Macedonians and Thracians covered their horses with the skins of these beasts, as we can still see in stone reliefs, which have been preserved.