There is an SF story, mid-1960s vintage or perhaps earlier, in which a time-traveling scientist is sent back from his own present to board the sealed train carrying Lenin back to Russia to carry out the Bolshevik revolution. The idea is that by assassinating Lenin, the Soviet Union will be removed from human history.  The scientist (disguised as an Imperial German officer) kills Lenin and returns to his own time and place (he was launched from the lawn of the White House) to discover that his own present is dramatically altered -- the Third Reich won World War II.

It's strange that I can remember so much of the plot, and can't recall the title or author of the story. Y'all's help is greatly appreciated.

I don't remember a book with that plot but it sounds remarkably like an episode of Star Trek Enterprise.  Do you remember anything of what the cover of the book you read looked like?

Tom:  I don't know the book you are seeking, but I can steer you to one of those "alternate histories" ,a post-WW II novel set in Germany, victors in that war.  It is Fatherland, by Robert Harris.

Not sure either, but I did like Fatherland.