This trait ennobles the U.S. military, but also makes it highly vulnerable to taking on undoable tasks.
The dirty fist in the young surgeon's pocket was obliged to undoable itself, and come out of its ambush disarmed.
Old English undon "to unfasten and open" (a window or door), "to unfasten by releasing from a fixed position," from un- (2) + do (v.). The notion is of "to annul something that was done." Related: Undone; undoing.