The mid-1940s to the early 90s was a period of high tension for most of the world, with the Eastern and Western Blocs building up a ridiculous amount of nuclear weapons in case the tension stopped. This left quite an impression. You're probably looking for one of these tropes:

* UsefulNotes/ColdWar, for works set during this period
* UsefulNotes/HistoryOfTheColdWar, a detailed breakdown of the war
* SpaceColdWar, for any cold war other than the historical conflict (and often, though not necessarily, set in space)
* EnforcedColdWar, where the war is kept cold by a higher power
* LensmanArmsRace, an arms race which escalates into cosmic levels of destruction

Not to be confused with:
* EscalatingWar, where two individuals emulate the LensmanArmsRace without actual weapons

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