It is quite interesting to examine the details of Alexander's army. The main body consisted of six brigades of 3000 men, each united to form an irresistible phalanx. Heavily armoured, with a long shield, a long sword, and a four-and-twenty foot spear (sarina), the infantryman of the phalanx must have possessed a powerful physique to enable him to carry himself and his weapons in the field. The depth of the phalanx was sixteen ranks, and the first six ranks were so placed that they could all bring their spears into action at once. The bulk of the phalanx consisted of Macedonians only. The light infantry, bowmen, and dartsmen numbered about 6000. A third corps of 6000 men more lightly armed, but with longer swords than the phalangists (called Hypaspists), were intermediate. The cavalry consisted of three classes, light, heavy, and medium, 3000 Macedonian and Thessalian horsemen, heavily armoured, forming its main strength. The light cavalry were Thracian lancers. The Royal Horse Guard included eight Macedonian squadrons of horsemen picked from the best families in Greece. It is useful to note that there were mounted infantry and artillery (_i.e._ balistai and katapeltai) with the force. More useful still to note that none of Alexander's victories were won by the solid strength of his phalanx; it was the sweeping and resistless force of his cavalry charges (often led by himself) that gained them.
Perhaps the most notable feature about this Greek expedition to India was the fact that it was the first military expedition of which there is any record which included scientific inquiry as one of its objects. Alexander had on his personal staff men of literary if not of scientific acquirements, and it is to them doubtless that we owe a comparatively clear account of the expedition, although unfortunately their records have only been transmitted to us by later authors. If we could but recover originals what a host of doubtful points might be cleared up! It is true that previous to the date of Alexander one man of genius, Xenophon, had kept a record of a magnificent military achievement, and had proved himself to be master of literature as he was of the science of leading; but Xenophon stands alone, and it may be doubted whether, during the many centuries which have passed away since the era of Greek supremacy, any practical leader of men has ever attained such a splendid position in the ranks of writers of military history. Alexander appears, at any rate, to have been no historian, but his staff of cultivated literary assistants and men of letters included many notable Greek names.