Wu (222–280), commonly known as Eastern Wu or Sun Wu, was one of the three major states that competed for supremacy over China in the Three Kingdoms period (220–280). It previously existed from 220–222 as a vassal kingdom nominally under Cao Wei, its rival state, but declared independence from Wei and became a sovereign state in 222. It became an empire in 229 after its founding ruler, Sun Quan, declared himself 'Emperor'. Its name was derived from the place it was based in — the Jiangnan (Yangtze River Delta) region, which was also historically known as "Wu". It was referred to as "Eastern Wu" or "Sun Wu" by historians to distinguish it from other Chinese historical states with similar names which were also located in that region, such as the Wu state in the Spring and Autumn period and the Wuyue kingdom in the Five Dynasties and Ten Kingdoms period. It was called "Eastern Wu" because it occupied most of eastern China in the Three Kingdoms period, and "Sun Wu" because the family name of its rulers was "Sun". During its existence, Wu's capital was at Jianye (present-day Nanjing, Jiangsu), but at times it was also at Wuchang (; present-day Ezhou, Hubei).