The Greeks conquered all of Persia, but Alexander III kept the Persian system of governance in place. He appointed Macedonian generals as governors over the various provinces. In other cases, he appointed Persians or local warlords or even vassal kings over control of certain provinces. After Alexander died, he was succeeded by his son (who was too young to rule) and, later, his own brother (who was mentally handicapped). This meant the empire was in the control of a regent who ruled on behalf of a king not capable of ruling on his own. Alexander's Greek and Macedonian generals who were put in command of the various provinces went to war over the regency for years. Once both royal successors were dead, four or five of these governors all proclaimed themselves king of their respective regions. Meanwhile, the outer provinces like Bactria, Sogdia and India declared their independence from Persia. The various kingdoms remained in a state of perpetual war for decades while areas like Media (Iranian Plateau), Armenia, Cappadocia and Mesopotamia all gained their independence one after the other amid the turmoil. The Romans later came in and scooped up Greece, Macedonia, Asia Minor, Syria, Palestine and Egypt over the course of many decades.