context: Yan Xishan (or Yen Hsi-shan, IPA: [i̯ɛ́n ɕíʂan];) is a warlord who serves the government of the Republic of China. He effectively ruled Shanxi Province from the Xinhai Revolution in 1911 up to the Communist victory in the Chinese Civil War in 1949. During his leadership of a relatively small, poor and remote province, he was able to survive the intrigues of Yuan Shikai. , Era of War Leaders, Nationalist Era, Japanese invasion of China, and ongoing civil war. His power was only halted after the Nationalist army, which became its ally, completely lost control of mainland China, which isolated Shanxi from all sources of economic and military supplies. He was seen by Western biographers as a transitional figure who supported the use of Western technology to protect Chinese traditions, while at the same time changing political, social and economic conditions were paving the way for radical changes that took place after his rule. [1]
question: When was Yan Xishan appointed Chinese warlord?
answers.text: 1911