The expedition was launched mainly due to Tahmasp's own incompetence and ill-thought attempt at curbing the powers of his upstart general and military genius.

After the brief campaign in southern Khorasan that culminated in the battle of Sangan Nader was determined on a more ambitious plan of action which involved the taking of Herat in order to completely subdue the Abdali Afghans.

He thus agreed with his Monarch Tahmasp II that they would invade southward were their paths would converge, leading to the final destination of Herat.

He left his brother in Mashad and set off with the bulk of his men and pursued Tahmasp north where the Shah was joined by the Qarachoorloo Kurds.

After taming Tahmasp, Nader advanced on Astarabad, then further into Mazandaran bringing the southern coast of the Caspian sea under his control.