This Fantastic World 11.

Air Force Colonel and former astronaut Greg Darwin is visited by his old friend, Johnny. After talking, Greg reveals to Johnny a secret from his past. While serving in space intelligence, Darwin, along with another astronaut, Dick, was sent on a secret mission to a planet that had suffered a devastating nuclear war. On orders from the command, Greg and Dick were to find the remaining weapons on a depopulated planet, the analogues of which did not yet exist on Earth...