Could the course and outcome of World War II be changed redundantly? Possibly, since all you need is a professional, experienced time-traveling historical researcher. The task may not be quite that simple, however, so he had better be very, very careful ...
The Lebe Technique, a secret "weapon" developed by a theoretical physicist among ODESSA SS exiles fleeing war crimes prosecution in 1960 Argentina, requires endless experimental trials prior to sending an ex-SS officer back to 1939 Berlin along with a full-blown account of "actual" WWII for use in some unknown way to "coach" a German victory.
Berlin, renamed Welthaupstadt Germania, the capital of Germany's neo-Nazi Empire by Hitler after the Third Reich caps its "War of World Liberation" by creating numerous foreign provinces, and becoming the seat of Neo-Nazi Germany's Empire. During imperial year 142, dating from 1933 when the vilified Nazi régime was born, veteran time-traveling Professor James Silverthorne of Goebbels Institut, once the University of Colorado in grossly swollen Greater Denver Gauleitung, the capital of Colorado-Provinz, is vetted by Nazi officialdom to undertake a hazardous retro-temporal research junket in millennia-distant European antiquity.
But local counter-dissidence Sicherheitsdienst investigators penetrate an allied revolutionary cell, and arouse suspicion that Silverthorne also members among the patriotic conspirators scheming to overthrow the Neo-Nazi empire, thus forcing his emergency retro-temporal return to the early months of WWII with an assignment to locate, hinder, thwart, or simply eliminate imperial hero of heroes Erich Lustmann, who by some totally unknown means has imitated Nostradamus and is beginning to influence a WWII victory by Nazi Germany.
Fearing his "mission impossible" to find Lustmann in bustling, wartime Berlin is precisely that, Silverthorne pursues his redundant world-changing crusade in an exciting time-travel adventure grand in scope and purpose.