What did Ahmad Shah Durrani do with the Mughal princesses?

I assume this question is referring to the events that took place during the Durrani invasion of the Mughal Empire, and subsequent capture of Delhi, in 1757. This invasion was one of multiple invasions of the declining Mughal Empire led by Ahmad Shah Durrani. Each one gradually pushing deeper into the center of the Mughal Empire.

Map of the Durrani Empire at its greatest extent. The Mughal Empire by this time was a shadow of its former self.

There is no doubt that death and destruction followed the capture of Delhi by the Afghan forces. A large tribute was levied upon the citizens of Delhi (both the nobility and the common folk) by Ahmad Shah Durrani. Not even the Mughal royal family was spared. The collectors would go house to house to collect all they could find. Under the pain of torture, if the need arose. Many were killed or taken as slaves during the Durrani occupation of Delhi. Those who were unable to pay the tax would often take their own lives. There was also unauthorized looting of houses by the soldiers. The city was plundered till little wealth remained. The Hindu population of the city seems to have suffered more so than the Muslim population.

However, Ahmad Shah Durrani did not do anything extraordinarily nefarious to the Mughal Shehzadi (princesses). Despite what some people seem to claim. They were not sold as sex slaves as another answer claims. The Mughal princesses were royalty who belonged to one of the most respected dynasties (Timurid or Gurkani) in the Islamic world. They would have treated in a manner befitting their station. Inflicting any harm to them would have harmed Ahmad Shah’s own image and reputation. Ahmad Shah was not foolish enough to do anything of the sort.

The Mughal capital of Delhi was nothing like it had been at the peak of the empire. The city had already been plundered by Nader Shah Afshar only a few years prior. Infighting among the Mughal dynasty and nobility had caused further decline in status and power for the city. Ahmad Shah Durrani’s plunder of the city was just another blow to its prestige and wealth. It would be plundered in the future by both the Maratha and British Empires as well.

Ahmad Shah Durrani would arrange marriages between the Mughal Dynasty and his own during this time. The purpose of which was to elevate his own status and that of his dynasty. Ahmad Shah was a monarch who had risen to power by his own ability. He did not belong to any royal dynasty. This was actually quite common among the rulers who had recently risen to power. Nader Shah Afshar had done the same by marital connections with and a Mughal and Safavid princess. Remember that the Timurids themselves had done the same in their early years by marriages to Chingizid Khanum (princesses). Hence, the dynastic name of Gurkani (Royal Son-in-Law of Genghis Khan).

This was not the first time Ahmad Shah had formed marital connections with the Mughal Dynasty to elevate his own status. He had previously married Iffat-un-Nissa Begum, a Mughal princess and widow of an Afsharid prince. During his stay at Delhi, Ahmad Shah would force the Mughal princess Hazrat Begum, daughter of the former Mughal Emperor Muhammad Shah Rangeela, to marry him. Despite strong opposition to the marriage from both her and her mother. A marriage was also arranged between his son, Timur Shah Durrani, and Gauhar Begum (also known as Zuhra Begum), daughter of Mughal Emperor Alamgir II. Such marriages were common enough among the nobility within the Islamic world. The two Mughal princesses, accompanied by other members of the Mughal harem, travelled with Ahmad Shah westwards back to his capital.