When the war broke out, Munro refused a commission joined the British armed forces as a regular trooper where he was certain to see battle. He was killed in action by a German sniper. His last words were reported as, "Put that bloody cigarette out!" In one of those unfortunate twists of fate, the papers that Munro had left behind were destroyed by his sister Ethel, who wrote her own account of their childhood. Murno never married and may have been gay, but homosexuality was a crime in Britain during Munro's lifetime and the decorum of the times would have required him to keep that part of his life secreted away.

Munro had a penchant for mocking the popular customs and manners of Edwardian England. He often did so by depicting characters in a setting and manner that would contrast their behavior with that of the natural world; often demonstrating that the simple and straightforward rules of nature would always trump the vanities of men. This is demonstrated gently in The Toys of Peace where parents from Edwardian England are taught a lesson that is still familiar to modern parents. And it is demonstrated with striking clarity in the highly recommended story The Interlopers. The Open Window is a fine example of his more humorous work is a highly recommended read.