The ancient Chinese system of government evolved from feudalism to a centralized imperial system. During the Shang dynasty, China was ruled as a feudal system with the king controlling the capital area and dividing the rest of the land into feudal states governed by feudal lords (shi) who paid tribute. The Qin dynasty defeated the other states and created China's first centralized empire with a unitary system of government characterized by direct control over provinces through governors. The Mandate of Heaven established the belief that heaven blessed wise rulers and people could overthrow rulers who lost heaven's mandate. The Han dynasty introduced civil service exams to recruit officials based on merit rather than birth.