Delhi Sultanate refers to the various Muslim dynasties that ruled in India (1210-1526). It was founded after Muhammad of Ghor defeated Prithvi Raj and captured Delhi in 1192. In 1206, Qutb ud-Din, one of his generals, proclaimed himself sultan of Delhi and founded a line of rulers called the Slave dynasty, because he and several of the sultans who claimed succession from him were originally military slaves. Iltutmish (1210-35) and Balban (1266-87) were among the dynasty's most illustrious rulers. Constantly faced with revolts by conquered territories and rival families, the Slave dynasty came to an end in 1290. The sultanate was in constant flux as five dynasties rose and fell: Mamluk or Slave (1206-90), Khalji (1290-1320), Tughluq (1320-1413), Sayyid (1414-51), and Lodi (1451-1526). Under the Khalji dynasty (1290-1320), the conquests of Ala ud-Din Khalji brought Muslim dominion in India to its greatest height until the Mughul empire. Early in the reign of Muhammad Tughluq, founder of the Tughluq dynasty (1325-98), the power of Delhi was acknowledged even in the extreme S of India. His eccentric rule and ferocious temperament provoked a series of revolts, notably that of the Hindu Vijayanagar kingdom in the south, and a steady loss of territory; by his death (1351) the Hindu south had recovered its independence and the Deccan had become a separate Muslim state, the Bahmani kingdom. Under Tughluq's successors the sultanate of Delhi began to disintegrate into several small states. With the sack of Delhi by Timur in 1398, the once great sultanate fell, although local rulers lingered on at Delhi until the invasion of Babur and the Mughal conquest. Both the Quran and sharia (Islamic law) provided the basis for enforcing Islamic administration over the independent Hindu rulers, but the sultanate made only fitful progress in the beginning, when many campaigns were undertaken for plunder and temporary reduction of fortresses. The effective rule of a sultan depended largely on his ability to control the strategic places that dominated the military highways and trade routes, extract the annual land tax, and maintain personal authority over military and provincial governors. Sultan Ala-ud-Din made an attempt to reassess, systematize, and unify land revenues and urban taxes and to institute a highly centralized system of administration over his realm, but his efforts were abortive. Although agriculture in North India improved as a result of new canal construction and irrigation methods, including what came to be known as the Persian wheel, prolonged political instability and parasitic methods of tax collection brutalized the peasantry. Yet trade and a market economy, encouraged by the free-spending habits of the aristocracy, acquired new impetus both inland and overseas. Experts in metalwork, stonework, and textile manufacture responded to the new patronage with enthusiasm.