...By that, I mean 1906.
When the US acquired Mindanao after the beating Spain in the Spanish-American war, Americans came face to face with what came to be known as asymmetrical warfare. Here were attacks on civilians, beheadings, raids on schools. All the stuff of modern headlines. And in the pre-explosive era the ultimate weapon of Imams was the suicide bomber of the day: the juramentado.
Check out the whole thing at The Belmont Club.