foundations. Numerous copper plate inscriptions from India as well as Tibetan and Chinese texts suggest that the patronage of Buddhism and Buddhist monasteries in medieval India was interrupted in periods of war and political change, but broadly continued in Hindu kingdoms from the start of the common era through the early first millennium CE. The Gupta kings built Buddhist temples such as the one at Kushinagara, and monastic universities such as those at Nalanda, as evidenced by records left by three Chinese visitors to India. Internal social-economic dynamics According to some scholars such as Lars Fogelin, the decline of Buddhism may be related to economic reasons, wherein the Buddhist monasteries with large land grants focused on non-material pursuits, self-isolation of the monasteries, loss in internal discipline in the sangha, and a failure to efficiently operate the land they owned. With the growing support for Hinduism and Jainism, Buddhist monasteries also gradually lost control of land revenue. Turkic invasions and conquest (10th to 12th century) Invasions According to Peter Harvey: The Muslim conquests in the Indian subcontinent was the first great iconoclastic invasion into the Indian subcontinent. As early as the 8th century, Arab conquerors invaded present-day Pakistan. In a second wave, from the 11th through the 13th centuries, Turkic, Turkic-Mongolian and Mongolian overtook the northern Indian plains. The Persian traveller Al Biruni's memoirs suggest Buddhism had vanished from Ghazni (Afghanistan) and medieval Punjab region (northern Pakistan) by early 11th century. By the end of the twelfth century, Buddhism had further disappeared, with the destruction of monasteries and stupas in medieval north-west and western Indian subcontinent (now Pakistan and north India).<ref name="Mcleod">McLeod, John, The History of India, Greenwood Press (2002), , pp. 41–42.</ref> The chronicler of Shahubuddin Ghori's forces records enthusiastically about attacks on the monks and students and victory against the non-Muslim infidels. The major centers of Buddhism were in north India and the direct path of the armies. As centers of wealth and non-Muslim religions they were targets. Buddhist sources agree with this assessment. Taranatha in his History of Buddhism in India of 1608, gives an account of the last few centuries of Buddhism, mainly in Eastern India. Mahayana Buddhism reached its zenith during the Pala dynasty period, a dynasty that ended with the Islamic invasion of the Gangetic plains. According to William Johnston, hundreds of Buddhist monasteries and shrines were destroyed, Buddhist texts were burnt by the armies,