A major event in early Spanish colonization, which had so far yielded paltry returns, was the Spanish conquest of the Aztec empire (1519-1521). It was led by Hernán Cortés and made possible by securing indigenous alliances with the Aztecs' enemies, mobilizing thousands of warriors against the Aztecs for their own political reasons. The Aztec capital, Tenochtitlan, became Mexico City, the chief city of the "New Spain". More than an estimated 240,000 Aztecs died during the siege of Tenochtitlan, 100,000 in combat, while 500–1,000 of the Spaniards engaged in the conquest died. The other great conquest was of the Inca empire (1531-35), led by Francisco Pizarro.