(early summer of 334 BC), first victory won by Alexander the Great of Macedon in his invasion of the Persian Empire. The best account in the ancient sources, which include Diodorus Siculus (1st century BC) and Plutarch's Life of Alexander (2nd century AD), is that of Arrian's Anabasis (2nd century AD), which draws directly from contemporary accounts. The Persian army, numbering perhaps 40,000, occupied the far bank of the Granicus River (present-day Kocabaş, which flows into the Sea of Marmara). Alexander sent his shock troops, the Companions, into the stream to attack the Persians, who drove back the assault. When the Persians entered the stream to pursue the Macedonians, Alexander led the remaining Companions obliquely into the confused Persian ranks. The Persian cavalry fled, leaving the Greek mercenaries, who were on the plain along the river, open to a devastating assault from Alexander's army. Alexander himself killed two relatives of the Persian king, Darius III, and his own life was saved by his cavalry commander, Cleitus (the Black). According to Arrian, Alexander lost only 115 of his own men. The victory left Asia Minor wide open to the Macedonian invasion.