How did Iltutmish save his kingdom from the Mongol threat?

Iltutmish used diplomacy to save his kingdom from the threat of Mongol invasion. In 1221, Mongol leader Changez khan conquered many parts of Central Asia. Chasing the ruler of Khawarizm, the Mongols came right upto the bank of the Indus river and threatened Iltutmish's empire. The ruler of Khawarizm requested Iltutmish to provide him shelter. But sensing the danger of Mongol attack on his empire, he diplomatically refused him shelter. This pleased Changez Khan, who went back without attacking Iltutmish's empire.