The Byzantine–Sasanian War of 602–628 was the final and most devastating of the series of wars fought between the Byzantine Empire and the Sasanian Empire of Iran. This became a decades-long conflict, the longest war in the series, and was fought throughout the Middle East: in Egypt, the Levant, Mesopotamia, the Caucasus, Anatolia, Armenia, the Aegean Sea and before the walls of Constantinople itself. While the Persians proved largely successful during the first stage of the war from 602 to 622, conquering much of the Levant, Egypt, several islands in the Aegean Sea and parts of Anatolia, the ascendancy of the emperor Heraclius in 610 led, despite initial setbacks, to a status quo ante bellum. Heraclius' campaigns in Iranian lands from 622 to 626 forced the Persians onto the defensive, allowing his forces to regain momentum. Allied with the Avars and Slavs, the Persians made a final attempt to take Constantinople in 626, but were defeated there. In 627, allied with Turks, Heraclius invaded the heartland of Persia.