High Quality Content by WIKIPEDIA articles! The Byzantine–Sassanid War of 602–628 was the final and most devastating of the series of wars fought between the Roman (Byzantine) Empire and the Sassanid Empire. The previous war had ended in 591 after Emperor Maurice had helped the Sassanian king Khosrau II regain his throne. In 602, Maurice was murdered by his political rival Phocas. Khosrau proceeded to declare war, ostensibly to avenge Maurice`s death. This war was a decades-long conflict, the longest single war in the series, and was fought throughout much of the Middle East and parts of Eastern Europe: in Egypt, the Levant, Mesopotamia, the Caucasus, Anatolia, and even before the walls of Constantinople itself.