ALEXANDER'S ARMY AT THE BEGINNING OF THE EXPEDITION (334)

Even the lost primary historians disagreed on the exact number of troops in Alexander's army: According to Anaximenes of Lampsacus (FGrH 72 F29), there were 43,000 infantry and 5,500 cavalry; Ptolemy son of Lagus (FGrH 138 F4) gives 30,000 infantry and 5,000 cavalry; and Aristobulus of Cassandreia (FGrH 139 F4) 30,000 foot and 4,000 horse. The only writer who breaks down the figures into contingents is Diodorus (17.17.3-4), whose numbers may come directly from Cleitarchus: the 32,000 infantry are broken down into 12,000 Macedonians, 7,000 allies, 5,000 mercenaries, 7,000 Odrysians, Triballians, and Illyrians, and 1,000 Agrianes and archers; of cavalry there were 1,800 Macedonians, an equal number of Thessalians, 600 allies, and 900 Thracians and Paeonians (that is, 5,100, though Diodorus wrongly gives a total of 4,500). Plut. Alex. 15.1 gives 43,000 infantry and 5,000 cavalry; Front. Strat. 4.2.4 simply gives a round figure of 40,000 for Alexander's army. The lower figures for the army as a whole may not include those forces which had been in Asia since the spring of 336; Polyaenus 5.44.4 speaks of 10,000 men with Parmenion and Attalus.

PERSIAN NUMBERS AT THE GRANICUS RIVER (334)

Diodorus estimates the Persian forces at 10,000 cavalry and 100,000 infantry. Justin (11.6.11), probably the least reliable extant source, says that the Persian army numbered 600,000, but the Latin sescenta milia can mean simply “many thousands,” somewhat like the English hyperbole “millions.”