Nader Shah's invasion of India

In May 1738, Nader Shah, the ruler of Iran (1736–1747) and the founder of the Afsharid dynasty, invaded Northern India, eventually sacking Delhi in March 1739. His army easily defeated the Mughals at the Battle of Karnal and then occupied the Mughal capital.

Nader Shah's victory against the weak and crumbling Mughal Empire in the far east meant that he could afford to turn back and resume war against Persia's archrival, the neighbouring Ottoman Empire, as well as launch further campaigns in the North Caucasus and Central Asia.

The loss of the Mughal treasury, which was carried back to Persia, dealt the final blow to the effective power of the Mughal Empire in India.

By the end of 1736, Nader Shah had consolidated his rule over Iran and dealt with the internal uprisings that had developed over the three years before that. He now shifted his focus towards the Afghan Ghilji tribe, who had been reorganised by their new leader Hussain Hotak (r. 1725–1738), a cousin of Ashraf Hotak. By the middle of the 1730s, Hussain Hotak had built up a substantial power base as the ruler of Herat and had been striving for some years to weaken Nader Shah's authority over present-day Afghanistan. By April 1737, Nader Shah had gone east and established his camp at a location close to the city Kandahar, where he ordered the construction of a city named Naderabad. He soon defeated Hussain Khan and captured Kandahar, thus putting an end to the Ghilji tribe's dominance. On 21 May 1738, Nader Shah left Naderabad and marched towards the city of Kabul. On 11 June, he reached Ghazni after crossing the traditional border between Iran and the Mughal Empire.

At first, Nader Shah told the Mughals that he had no issues with them and he only moved into their domain to look for runaway Afghans. According to some contemporary Indian sources, the Mughal vassals plotting to weaken the authority of their suzerain were the reason behind Nader Shah's invasion of the Indian subcontinent. According to the Iranologist Laurence Lockhart, Nader Shah understood that he could fund his aspirations of expansion "with the spoils of India" because "the almost continual campaigns of the past few years had caused famine in Persia and brought her to the verge of bankruptcy." However, another Iranologist, Ernest S. Tucker, argues that "Long before the 1730s, though, Iran had already been in a state of financial crisis, partly because of the continued steady decline in Iranian exports that had caused a substantial reduction in state revenues." According to the Iranologist Michael Axworthy, the reason for the invasion was that Nader Shah "needed a breathing space, for the country to recover, and a new source of cash to pay the army, before he renewed his attack on the Ottomans."

By the start of the 18th century, the Mughals were struggling with a number of political issues. Their empire started to fragment after the death of the Mughal Emperor Aurangzeb in 1707, eventually becoming a collection of kingdoms ruled by individuals who claimed nominal allegiance to the Mughal Emperor Muhammad Shah (r. 1719–1748), but essentially acted as independent rulers. Another political danger was the expansion of the Maratha Empire under Bajirao I. By challenging long-held beliefs about the necessity of Muslim political power in India, the Marathas presented a unique challenge to Mughal rule. By the beginning of the 18th century, the Indian subcontinent was still a huge and prosperous agricultural economy, but becoming more and more politically divided, making it an alluring target for a conqueror short on finance.

Nader Shah crossed Mughal territory at the Mukhur spring and halted at Qarabagh, south of Ghazni. A detachment was sent under Nader's son, Nasrullah, to attack the Afghans of Ghorband and Bamian. When the governor of Ghazni fled upon hearing of Nader's approach, the Qadi, scholars and rich men of Ghazni gave the invaders presents and submitted to Nader when he entered on 31 May. Meanwhile, the other detachment had defeated the Afghans, pardoning all who surrendered, and exacting cruel punishment on those who resisted.

With his flank secure, Nader was free to march on Kabul. The chief men of the city tried to give in peacefully, but Sharza Khan decided to give resistance. On 10 June, Nader reached the city and the garrison sallied out to try and attack the Persians, who then just retreated to a safe distance where they could besiege the city. Nader arrived on the 11th and surveyed the city's defences from atop the Black Rock. The garrison tried to attack again, but were driven out by the Persian Army. The city was besieged for a week until on 19 June, the tower of Aqa-bin collapsed, and the citadel capitulated.