I'm curious where this phrase was even first used, and whether planners ever seriously took this promise, if it were made. It seems like a very arbitrary deadline that never would have made much sense, even logistically, should a war be short.

It seems like the phrase might have originated, at least in popular usage, with the fall 1950 offensives in the Korean War, although here again I'm not sure any officials actually made this promise, let alone thought the war would be so utterly over by late December that troops would be withdrawn. Does it have an older usage than this, I wonder?