Alan E Nourse's "Infinite Intruder" (novelette, grandfather paradox, free): When a man was his own grandfather!
Decent first half where suspense builds up; crappy second half where we are handed a lot of stuff about the pseudo-Physics & limitations of time travel.
Through the story, we'll see Eurasia destroyed in an "Atomic War" with the US, & a US Dictator beginning attacks on Mars inhabited by peaceful Martians who do have enormous resources.
Story summary.Some people have been trying kill the little son of Roger Strang, a man building some sort of "electronic Barrier" to protect the US from atomic war with "the Eurasian Combine". And local security people think Roger is mad & don't plan to investigate; in fact, they accuse him to be an impostor ... some kind of a spy planted in their midst!
Suspense will slowly reveal, but only after we're handed far too much crap on time travel technology & rules.
Fact sheet.First published: Space Science Fiction, July 1953.
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Related: Grandfather paradox in fiction; fiction from 1950s.