An invasion of Macedonia and Greece by Goths, who had been displaced from their lands on the Black Sea, was defeated by emperor Claudius II Gothicus at the Battle of Naissus in 268 or 269. Historians see this victory as the turning point of the crisis. In its aftermath, a series of tough, energetic barracks emperors were able to reassert central authority. Further victories by Claudius Gothicus drove back the Alamanni and recovered Hispania from the Gallic Empire. He died of the plague in 270 and was succeeded by Aurelian, who had commanded the cavalry at Naissus. Aurelian reigned (270–275) through the worst of the crisis, gradually restoring the empire. He defeated the Vandals, Visigoths, Palmyrene Empire, and finally the remainder of the Gallic Empire. By late 274, the Roman Empire had been reunited into a single entity. However, Aurelian was assassinated in 275, sparking a further series of competing emperors with short reigns. The situation did not stabilize until Diocletian, himself a barracks emperor, took power in 284.