Britain entered World War I in 1914 to honor a treaty that promised to defend Belgium and to fulfill an alliance with France and Russia. The Germans attacked Liege, Belgium, in the first battle of World War I, and then marched on to attack France.
I'm assuming by "war" you mean World War I
Inca were known for their cruelty and often killed people, but they would not be killed. Rather, they would be separated and sent to different regions, sometimes where other languages were spoken, to make it impossible for them to organise further rebellions.
Radical Republicans and Carpetbaggers