I'm trying to recall a sci-fi short story. The setting is during the Cold War on a space station orbiting Earth. The way the story is set up it seems as if the astronauts are American, and Russia has just launched a nuclear strike that has destroyed the USA. The two (I think there are two anyway) astronauts have the job of launching the counter strike from space to destroy Russia in retaliation. They then face the moral dilemma of whether or not to do this, and in the end make the choice not to launch the counter strike. It is then revealed that the astronauts (the "good guys" in this story) are actually Russian, and it is the USA who launched the initial strike.
I think the story was probably from around the 60s - someone like Heinlein or Asimov. Some of the details may well be wrong, as I only read it once, decades ago.