The
Western Zhou period (1046–771 BC) was the first half of the
Zhou dynasty of ancient China. It began when
King Wu of Zhou overthrew the
Shang dynasty at the
Battle of Muye. The dynasty was successful for about seventy-five years and then slowly lost power. The former Shang lands were divided into hereditary fiefs which became increasingly independent of the king. In 771,the Zhou were driven out of the
Wei River valley; afterwards real power was in the hands of the king's nominal vassals.