The River Granicus was a significant obstacle to Alexander the Great's progress and offered the Persians their best chance to halt his advance.
Having brought Greece under his control, Alexander of Macedon launched a campaign into Asia Minor. This was opposed by the Persian Satraps whose territory was threatened, assisted by a Greek mercenary commander, Memnon of Rhodes. Memnon suggested a delaying strategy in the hope that the Macedonians' supplies would run out, but was overruled.
The Persian army moved to intercept Alexander's expedition and established a blocking position at the Granicus River, which could only be crossed by an army at certain points. The Persian force was superior in cavalry and drew up with its cavalry to the fore. The infantry, composed mainly of Greek mercenaries, was placed in support.
Disregarding suggestions of a more cautious strategy made by his subordinates, Alexander decided to force a crossing. His attack opened with a feint by his right-flank forces which drew Persian reinforcements off to their left flank.
Alexander personally led the attack on the Persian centre while his left-flank formations also advanced. The Persians initially held the advantage, defending a steep riverbank while their opponents had to struggle across the river and then attack uphill. The Macedonians' long spears gave them an advantage over the Persian cavalry, and the fight increasingly turned in Alexander's favour once his troops reached more level ground.
As the Persians were pushed back, Alexander himself was a prime target for their best cavalry. Indeed, it has been suggested that the crux of the Persian strategy was to kill him, which would likely cause the Macedonian army to fall apart. The attempt almost succeeded, but eventually, the Persian centre gave way. The flanks soon followed, leaving only the Greek mercenaries to oppose the Macedonian advance.
The Greeks Fight On
Abandoned by their cavalry, the experienced Greek mercenaries were unable to withdraw but made a stubborn stand. Their request for surrender terms was denied, with Macedonian attacks continuing until the mercenaries agreed to an unconditional surrender. With the Persian army scattered and his own forces now established across the river, Alexander was able to resume his march into Asia Minor. The Battle Of Leuctra: The Theban Army Defeats The Spartans & Kills Their King In 371 BCE.