After the death of Spitamenes and his marriage to Roxana to cement his relations with his new Central Asian satrapies, Alexander was finally free to turn his attention to the Indian subcontinent. Alexander invited all the chiefs of Gandhara, in the north of what is now Pakistan, to come to him and submit to his authority.
Omphis, whose kingdom extended from the Indus to the Hydaspes, complied, but the chiefs of some hill clans,refused to submit.
In the winter of 327/326 BC, Alexander personally led a campaign against these clanes.
A fierce contest ensued with the Aspasioi in which Alexander himself was wounded in the shoulder by a dart but eventually the Aspasioi lost the fight. Alexander then faced the Assakenoi, who fought bravely and offered stubborn resistance to Alexander in the strong of Massaga, Ora and Aornos.
The fort of Massaga could only be reduced after several days of fighting in which Alexander himself was wounded seriously in the ankle.
According to Curtius, "Not only did Alexander slaughter the entire population of Massaga, but also did he reduce its buildings to rubbles".
A similar slaughter then followed at Ora, another stronghold of the Assakenoi. In the aftermath of Massaga and Ora, numerous Assakenians fled to the fortress of Aornos.
Alexander followed close behind their heels and captured the strategic hill-fort after the fourth day of a bloody fight.
After reducing Aornos, Alexander crossed the Indus and fought and won an epic battle against a local ruler Porus,in the Battle of Hydaspes in 326 BC.
Alexander was greatly impressed by Porus for his bravery in battle, and therefore made an alliance with him and appointed him as satrap of his own kingdom.
Alexander named one of the two new cities that he founded, Bucephala, in honor of the horse that had brought him to India, and had died during the battle.
Revolt of the Army
Worried about having to face other powerful Indian armies and exhausted by years of campaigning, refused to march further east. This river marks the easternmost extent of Alexander's conquests. Alexander spoke to his army and tried to persuade them to march further into India but, he change his opinion and return. Along the way his army conquered the Malli clans and other Indian tribes.
Alexander sent much of his army to Carmania (modern southern Iran) with his general Craterus, and commissioned a fleet to explore the Persian Gulf shore under his admiral Nearchus, while he led the rest of his forces back to Persia through the most difficult southern route along the Gedrosian Desert and Makran (now part of southern Iran and Pakistan).