True, most of the little-known wars were short and probably not very well-known when they were being fought, but there was one war, sort of considered two wars, that lasted from 1899 to 1913. Can you guess?
The first was called the Philippine-American war, and started when Spain lost the country to us, and we laid claim to it. Immediately, the revolt, which had been going on against Spain since 1896, transferred its hostilities to us, until we formally put it down in 1902. But it continued anyway, renamed the Moro Rebellion, till 1913, when the revolutionaries gave up. And we finally granted them full independence in 1946. How about that for an unknown war? Know of any other interesting ones?
All this is to introduce a piece on what's going on currently in the Philippines, with a lot of retrospective on the events I just recounted, and lots of great political cartoons of the war period, from the Unz Review [link]: