Kushans converted to Hinduism and Buddhism, and promoted these Indian religions throughout Central and South Asia. The region reached its height under the Buddhist ruler Kanishka the Great. After the fall of the Kushans, the region came under the control of the Gupta Empire of ancient India. During this period, Hindu and Buddhist art and architecture flourished in the area. With the decline of the imperial Guptas, the Hindu Shahis came to rule the area. The Hindu Shahis built two massive forts in the northern edges of Dera Ismail Khan. The forts were later renamed as "Kafirkots" (forts of the infidel). These Hindu Shahi forts were known for high towers and steep defensive walls. The Hindus also built many Hindu temples around the area, however, many of them are now in rubble. The Hindu Shahis remained in control of the area until their defeat by the Turkic Muslim army of Ghaznavids. The district is part of what was historically territory inhabited by the Baluch people during medieval India, who were invited to settle the region by Shah Husseyn, of the Langah Sultanate of Multan. These Baluch settlers were displaced by or assimilated into, later waves of Pashtun settlement. Dera Ismail Khan was created as an administrative unit of British India, part of the Derajat Division of the North-West Frontier Province. It was formerly divided into two almost equal portions by the Indus River, which intersected it from north to south. To the west of the Indus, the characteristics of the country resembled those of Dera Ghazi Khan. To the east of the present bed of the river, there is a wide track known as the Kachi, exposed to river action. Beyond this, the country rises abruptly, and a barren, almost desert plain stretches eastwards, sparsely cultivated, and inhabited by nomadic tribes. In 1901, the trans-Indus tract was allotted to the newly formed North-West Frontier Province, the cis-Indus tract remaining in the Punjab jurisdiction. The cis-Indus portions of the Dera Ismail Khan and Bannu districts now comprise the new Punjab district of Mianwali. Wheat and wool were exported. In 1901, it contained an area of and a population of 252,379. In 1947, it became part of the newly independent Pakistan. In 2016, 191,000 acres in the district were brought under cultivation with completion of the Gomal Zam Dam, and a series of irrigation canals partially funded by the United States Government.