Delhi became an important city only in the twelfth century. It was the capital of kingdom under Tomara Rajputs, who were defeated in the middle of 12th century by the Chauhans (also referred as Chahamanas) of Ajmer. Ananga Pala (Tomaras) of the Rajput Dynasty first established his capital at Delhi. The period from 1206 A.D. to 1526 A.D. came to be known as the Delhi Sultanate period. This period witnessed many dynasties and various rulers. Mongol attacks on the Delhi Sultanate increased during the reign of Alauddin Khalji and in the early years of Muhammad Tughluq’s rule.