Still, with the neutralization of Khosrau's most skilled general, Heraclius deprived his enemy of some of his best and most experienced troops, while securing his flanks prior to his invasion of Persia.[19] In the next year, Heraclius led an invasion into Mesopotamia once again, defeating another Persian army at Nineveh. Afterwards, he marched on to Ctesiphon where anarchy reigned allowing Heraclius to extract ever more favorable terms as one Persian king was overthrown by another. Eventually, the Persians were obliged to withdraw all armed forces and return Egypt, the Levant and whatever imperial territories of Mesopotamia and Armenia were in Roman hands at the time of an earlier peace treaty in c.