Any historical turning point is potentially a job for the Time Patrol although Poul Anderson avoided writing stories about obvious examples: Nazis winning World War II etc. He
did discuss how to prevent Hitler's birth and also mentioned the following twentieth century turning point:
"The Bolshevik Revolution of 1917 came near failing. Only the energy and genius of Lenin pulled it through. What if you traveled to the nineteenth century and quietly, harmlessly prevented Lenin's parents from ever meeting each other?"
-Poul Anderson, "The Year of the Ransom" IN Anderson, Time Patrol (Riverdale, NY, 2010), pp. 641-735 AT p. 672.
We recall this passage because we have acquired W. Somerset Maugham, Ashenden (London, 2000), fiction based on its author's experiences.
"In 1917 I went to Russia. I was sent to prevent the Bolshevik Revolution and to keep Russia in the war. The reader will know that my efforts did not meet with success."
-Preface, pp. v-x AT p. ix.
If Maugham had succeeded, then the Time Patrol would have had to become involved.
Since we have compared Anderson's Dominic Flandry with Ian Fleming's James Bond, we might also compare Bond with Maugham's Ashenden. Bond is a Cold War secret agent whose superior is an Admiral called M whereas Ashenden is a World War I secret agent whose superior is a Colonel called R.
We live in a sea of literary associations.