It was the Chinese who attacked first. The Uighurs are not Chinese and the area was never Chinese, but the Chinese Empire conquered it in the 18th century, committing genocide against another people in the region, the Dzungars. The Chinese then committed atrocities against the Uighurs, including mass rape of Uighur women (similar to what the Serbs did to the Bosniaks). Uighurs have wanted to be independent again pretty much ever since. A 19th century revolt, joined by a large part of the other large Muslim population in China, the Hui, succeeded for a few years, but was brutally crushed, with many of the survivors fleeing to Russia. (The Hui actually ARE Chinese and have played a major role in Chinese history; many Chinese military leaders have been Hui, and the founder of the Red Guards who played such a destructive role in the Cultural Revolution was Hui.)
And now the Uighurs are targets of genocide. John Bolton claims that Trump supported China rounding up the Uighurs into concentration camps. What would you do were you a Uighur?