 Nabopolassar attempted a counterattack, marched his army into Assyria proper in 616 BCE, and tried to besiege Assur and Arrapha (modern Kirkuk), but was defeated by Sin-shar-ishkun and chased back into Babylonia after being driven from Idiqlat (modern Tikrit) at the southernmost end of Assyria.A stalemate seemed to have ensued, with Nabopolassar unable to make any inroads into Assyria despite its greatly weakened state, and Sin-shar-ishkun unable to eject Nabopolassar from Babylonia due to constant rebellions and civil war among his own people.Nabopolassar's position, and the fate of the Assyrian empire, was sealed when he entered into an alliance with another of Assyria's former vassals, the Medes, the now dominant people of what was to become Persia.