I am trying to find a short story I read that stuck with me. I probably read it in the late 60's or early 70's. It was written first person from the President to the crew of a spaceship that was stationed behind the moon as part of a Mutual Assured Destruction strategy. Spoiler alert - it was assumed to be president of USA until last line when you realize it was from the President of the USSR and he asked them not carry out their mission since MAD apparenetly hadn't worked.
Does anyone remember name and author of this story?