The Shang was conquered by the Zhou, who ruled between the 11th and 5th centuries BCE, though centralized authority was slowly eroded by feudal warlords. Some principalities eventually emerged from the weakened Zhou, no longer fully obeyed the Zhou king, and continually waged war with each other in the 300-year Spring and Autumn period. By the time of the Warring States period of the 5th–3rd centuries BCE, there were only seven powerful states left.