Khorasan campaign of Nader Shah

Rebellion and separation

Revolts in Khorasan during the 1720s followed the Afghan revolt in the eastern provinces, which culminated in Mahmud Hotaki's victory at the battle of Gulnabad and the capture of Isfahan. A courtier named Malek Mahmoud Sistani made an accord with the Hotaki conquerors, agreeing to establish an independent kingdom in Khorasan in exchange for recognizing Mahmud as Shah. Sistani quickly subdued most of Khorasan, including Mashad. Nader, based at the fortress of Kalat with 1,200 men, raided Sistani's territory without direct confrontation, positioning himself as the sole challenge to Sistani's influence.

Tahmasp II and the siege of Mashad

After the siege of Isfahan, Mahmud sent Afghans to subdue Qazvin, where Tahmasp had proclaimed himself Shah. Tahmasp fled westward but, with Ottoman forces advancing, reached Astarabad and allied with the Qajar warlord Fathali Khan. Deciding to begin in Khorasan, they marched there and gained the loyalty of Nader, whose force had grown through campaigns against the Kurds. A combined army of 30,000 men besieged Mashad, trapping Sistani and his commander Pir Mohammad.

Tensions between Tahmasp and Fathali Khan escalated when Nader presented an intercepted letter showing secret communication between Fathali and Sistani. Nader advised sparing Fathali, but Tahmasp executed him the next day. The Qajar contingent remained, and the siege ended when Pir Mohammad allowed Nader to infiltrate the city walls, forcing Sistani to surrender.

Aftermath of the siege

Malek Mahmoud Sistani was treated with courtesy and allowed to live as a sage, though he was executed the following year when he became suspect. The siege gave Tahmasp control of Mashad and elevated Nader to Fathali's position. Nader then subdued the remaining Khans and tribes of Khorasan, further augmenting his forces. The conquest allowed the Safavid loyalists to turn toward an expedition east to Herat.

Battle of Sangan

In 1727 Nader besieged and conquered Sangan. An Abdali army of 7–8,000 men marched to relieve the fortress.

Nader sent a force to the village of Niazabad, where the battle lasted four days. His men fought from trenches while 500 cavalry maneuvered against the Abdalis. The Abdalis withdrew to Herat, but Nader did not pursue, instead returning to Mashhad due to his insecure position.