The Inca civilization had unified a vast territory in South America integrating many ethnic groups into a unifiedsociety under the rule of a common Inca law. The arrival of the Spaniards stopped the development of this civilization and created a social gap that has endured for more than 500 years. The Incas resisted the conquerors for four decades until 1572 when Tupac Amaru, son of Manco Inca and the last Inca ruler, was executed along with his family and advisers, leaving no successor.