There was a story years ago that followed a group of survivors of a war. Before the conflict they sealed themselves inside a fully equipped cavern and waited out the conflict, only emerging when it was safe. they emerged and began to set up civilization while as scavenging off old military bases. i remember them finding planes underground and flying them.
already looked at all the stories on this previous thread:https://storiesonline.net/d/s4/t2272/post-apocalypse-coming-war-global-warming#po49159 but it wasn't any of them.