Wu (Chinese: 吳; pinyin: Wú; Middle Chinese *ŋuo < Eastern Han Chinese: *ŋuɑ), known in historiography 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 "Dong Wu" ("Eastern Wu") or "Sun Wu" by historians to distinguish it from other Chinese historical states with similar names which were also