The National Protection War breaks out against the Empire of China, as military leaders Cai E and Tang Jiyao proclaim the independence of Yunnan and begin a campaign to restore the Republic.

The National Protection War, also known as the Anti-Monarchy War, was a civil war that took place in China between 1915 and 1916. Following the overthrow of the Qing dynasty three years previously, the Republic of China was established in its place. The war was caused by President Yuan Shikai's proclamation of the Empire of China, with himself as the Hongxian Emperor.

The Empire of China, also known in historiography as the Hongxian Monarchy, was a short-lived attempt by Chinese president Yuan Shikai from late 1915 to early 1916 to reinstate the monarchy in China, with himself as emperor. The attempt ultimately failed, set back the republican cause by several years, and led China into a period of fracture and conflict among various local warlords.

Cai E (simplified Chinese: 蔡锷; traditional Chinese: 蔡鍔; pinyin: Cài È; Wade–Giles: Ts'ai⁴ O⁴; 18 December 1882 – 8 November 1916) was a Chinese revolutionary leader and general. He was born Cai Genyin (Chinese: 蔡艮寅; pinyin: Cài Gěnyín) in Shaoyang, Hunan, and his courtesy name was Songpo (Chinese: 松坡; pinyin: Sōngpō). Cai eventually became an influential warlord in Yunnan (Yunnan clique), and is best known for his role in challenging the imperial ambitions (Hongxian emperor) of Yuan Shikai during the Anti-Monarchy War.