Battle of the Granicus
Even if an uncontested crossing elsewhere was possible, it might have induced the Persian army to retreat. In that case Alexander would have lost the opportunity to quickly destroy the only Persian army present in Asia Minor at that time. An attack in the afternoon would also have meant that the Persians would have to fight with the sun in their eyes, whereas the Macedonians would have the sun in their eyes if they had attacked at dawn.

Casualties: 

Macedonian army: For the Macedonians, Arrian gives losses of 25 Companion cavalry in the preliminary attack, 60 from the rest of the cavalry and 30 of the infantry, a total of 115 killed. Plutarch gives 34 dead, of which 25 were cavalry and 9 were infantry. Justin mentions 9 infantry and 120 cavalry killed.
A. M. Devine observes that the source used by Arrian for the casualties was Ptolemy I, who in turn used Callisthenes as a source for the casualties. Plutarch used Aristobulus as his source. This suggests that Plutarch misunderstood the information, because his 25 dead cavalry are probably the 25 Companions who fell during the preliminary attack. Justin's figures seem to be a confused conflation of both Ptolemy I and Aristobulus. Because the battle was short, A. M. Devine considers Arrian's numbers to be reasonably accurate.

Persian army: Next to the Persian nobles who fell in personal combat with Alexander, many Persian leaders perished in the battle. Arrian mentions Niphates, Petenes, Mithrobuzanes, the satrap of Cappadocia, Arbupales, the son of the Darius who was the son of Artaxerxes II, Pharnaces, brother of the wife of Darius, and Omares. Arsites survived and fled into Phrygia, but committed suicide later because he was blamed for the defeat. Diodorus also mentions Atizyes, the satrap of Greater Phrygia as being killed, but also mentions him later as a casualty of the Battle of Issus.
For the Persians, Arrian states that 1,000 cavalry were killed and 2,000 Greek mercenaries were taken prisoner. Plutarch mentions 2,500 cavalry and 20,000 infantry killed. Diodorus gives statistics of 2,000 cavalry and 10,000 infantry killed, as well as 20,000 men who were taken prisoner. 
The casualty figures of Plutarch and Diodorus are judged to be impossibly large by A. M. Devine. He considers Arrian's figures of 1,000 cavalry killed and 2,000 captured Greek mercenaries to be reasonably accurate. He takes Arrian's number on the captured mercenaries to imply that the remaining 18,000 were killed, which he dismisses. Based on his theory that there were no more than 4,000 to 5,000 Greek mercenaries, it could possibly mean that 2,000 to 3,000 of them were massacred. This gives a total Persian loss of 5,000 to 6,000.

Aftermath: The 2,000 Greek mercenaries who were captured were sent to Macedon to work the land as slaves. Even though they were Greeks, Alexander felt they had betrayed their fellow Greeks with their service to the Persians. In doing so, they did not abide by the agreement made at the Hellenic League, which compelled the Greeks to fight Persia and not each other. He also sent 300 suits of Persian armour to Athens as a votive offering to Athena on the Acropolis. He ordered an inscription to be fixed over them so as to mark the absence of the Spartans in his united Greek army: "Alexander, son of Philip and all the Greeks except the Lacedaemonians, present this offering from the spoils taken from the barbarians inhabiting Asia". A statue group, known as the Granicus Monument, was erected by Alexander in the sanctuary of Zeus at Dion. This consisted of bronze statues by Lysippus of Alexander with twenty-five of his companions who had died in the initial cavalry charge, all on horseback. In 146 BC, after the Fourth Macedonian War, this statue group was taken to Rome by Quintus Caecilius Metellus Macedonicus, where they were displayed in a portico that he built below the Capitoline Hill.
Dascylium was evacuated by its Persian garrison and occupied by Parmenion. Alexander marched to Sardis, which surrendered to him. He continued to Ephesus, which was also evacuated by its garrison of Greek mercenaries. When Magnesia and Tralles also offered their surrender, he sent Parmenion to those cities. He sent Lysimachus to the cities in Aeolis and Ionia which were still under Persian control, ordering him to break up the oligarchies there and reinstate democratic government. When Alexander arrived at Miletus the city resisted him, so he besieged it.
The Persian military losses were not disastrous, as a large portion of the army managed to retreat to Halicarnassus. On the other hand, the strategic outcome was precarious for the Achaemenid Empire. Achaemenid satraps had been defeated in Asia Minor before and Sardis had been besieged, but this was the first time that the citadel of Sardis had fallen and that an enemy force could continue its march without significant obstacles until Halicarnassus.

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== Sources ==