China pops up a lot on this list. I'm just saying. This was a battle between the repressed Chinese minorities and the 19th century rulers of China. These people are still bitterly repressed by the larger Chinese ethnic groups, but lets not get into that now. The Hui and other Muslim ethnic groups in China had a tenuous peace with the Han people, and fears of Muslim raiders caused the Han to arm themselves, so the Hui armed themselves, and everyone got all antsy and boom, war broke out. These small local fights and battles coalesced into a centralized Muslim uprising against the Qing government, a war fought over 15 years, leading to millions of deaths.