The Zhou Dynasty conquered the Shang Dynasty in 1027 BCE and ruled over China until 256 BCE. They justified their conquest by claiming the Shang had lost the Mandate of Heaven, the divine right to rule granted by the gods. During the long Zhou rule, Chinese culture and technology advanced significantly through ambitious public works and the introduction of iron, money, and early forms of writing. However, over time the Zhou kings lost control of the feudal lords, leading to a period of political unrest and war between states vying for more power and territory.