The first Chinese dynasty that left historical records, the loosely feudal Shang (Yin), settled along the Yellow River in eastern China from the 17th to the 11th century BCE. The oracle bone script of the Shang Dynasty represents the oldest form of Chinese writing yet found, and is a direct ancestor of modern Chinese characters. The Shang were conquered by the Zhou, who ruled between the 12th and 5th centuries BCE, until its centralized authority was slowly eroded by feudal warlords. Many independent states eventually emerged from the weakened Zhou state, and continually waged war with each other in the 300-year-long Spring and Autumn Period, only occasionally deferring to the Zhou king. By the time of the Warring States period of the 5th–3rd centuries BCE, there were seven powerful sovereign states in what is now China, each with its own king, ministry and army.