In 328 BC, Alexander The Great of Macedonia and now the king of Persia, had conquered much of the former Satraps of the Achaemenid Empire up to Bactria. The remaining satraps lay in the Indus Valley, but Alexander ruled off invading the Indus until his forces were in complete control of the newly acquired satraps. In 327 BC, Alexander married Roxana (a princess of the former Bactria satrapy) to cement his relations with his new territories. Now firmly under Macedonian rule, Alexander was free to turn his attention to the Indus Valley. The rationale for the Indus campaign is usually said to be Alexander's desire to conquer the entire known world, which the Greeks thought ended around the vicinity of the River Indus.