Straight Dope Staff Report: Did the U.S. plan an invasion of Canada in the 1920s?

War Plan Red was a US Army planning exercise for possible war with Britain. The first move would be to strike at Canada and cut the UK’s bridgehead on the continent. Right up until 1939 it was unthinkable for the US army to contemplate a war in Europe because of isolationism, though they did plan for a Pacific war.