The Warring States period was an era in ancient Chinese history characterized by warfare, as well as bureaucratic and military reforms and consolidation. It followed the Spring and Autumn period and concluded with the Qin wars of conquest that saw the annexation of all other contender states, which ultimately led to the Qin state's victory in 221 BC as the first unified Chinese empire, known as the Qin dynasty. Although different scholars point toward different dates ranging from 481 BC to 403 BC as the true beginning of the Warring States, Sima Qian's choice of 475 BC is the most often cited. The Warring States era also overlaps with the second half of the Eastern Zhou dynasty, though the Chinese sovereign, known as the king of Zhou, ruled merely as a figurehead and served as a backdrop against the machinations of the warring states. The "Warring States Period" derives its name from the Record of the Warring States, a work compiled early in the Han dynasty.