Prime Minister David Lloyd George of Great Britain had advocated for harsh reparations from the defeated Germans in the aftermath of World War I. It was generally felt those reparations helped create the conditions which Hitler was later able to exploit for his own rise to power, years later. Hitler was able to tap into the anger the German people felt over the reparations forced on their nation.
The power-mad Hitler used the Nazi party as a tool for governmental domination. Hitler's ruthlessness would be historically compared to others, such as Alexander the Great, Genghis Khan, Julius Caesar, Napoleon Bonaparte, Maltuvis, Ferris, Krotus, Lee Kuan, Khan Noonien Singh, Immea of Kaveran, Baravis the Incomparable and the Vulcans of the Last-of-all-Cities colony. Hitler's regime initiated the attempted systematic genocide of Humans of Jewish descent—the Holocaust, which led to the deaths of millions of Jews alongside millions of other enemies of his government. (TOS episodes: "What Are Little Girls Made Of?", "Patterns of Force", "Whom Gods Destroy"; EV comic: "Cloak and Dagger"; TNG novel: Survivors; historical accounts)
In the late 1930s, Hitler and the Nazis turned their aggression outward when they began the conquest of Europe. Hitler tried to justify this in 1938, attributed with saying "We need breathing room". In 2293, the Klingon General Chang would unintentionally paraphrase Hitler, leading James T. Kirk to attribute the quote to Hitler's 1938 statement. (TOS movie, novelization & comic adaptation: The Undiscovered Country)
In the face of Hitler's aggression, other nations, including the Soviet Union, Great Britain, Canada, and later the United States formed an alliance to stop Hitler in his drive for conquest. These Allies drove the Nazis back to Germany and defeated them by 1945, but at a cost of millions of lives and large scale devastation of much of Europe and other Nazi-occupied lands. Hitler committed suicide in Berlin as Allied troops entered the city. (TOS episode & novelization: Patterns of Force)
For centuries to follow, it was debated whether the removal of Hitler from history would have prevented World War II. Leonard McCoy dismissed this idea, and the "one-man-as-catalyst" theory of history, arguing that war was part of the Human condition until the Human civilization outgrew it. (TOS novel: Strangers from the Sky)
In the 23rd century, historian Alexander Lazarus created an android replicant of Hitler on planet Gamma Alpha V, along with many other significant humans from throughout history. These extremely accurate copies were created with a machine, the psi-clone, that had the ability to create detailed scans of the minds of historical figures. (TOS comic: "The Legacy of Lazarus")
A Changeling once traveled back in time from the era of the 24th century, to a point just before the 1944 Normandy Invasion, attempting to change history by warning Adolf Hitler of the invasion. He was stopped by Jake Sisko and Nog. They were assisted by an ancestor of Jean-Luc Picard. (DS9 novel: Trapped in Time)
In various alternate timelines, Hitler was much more successful.
In one altered timeline, Hitler's government would receive assistance from the Na'kuhl—one of the alien factions fighting in the Temporal Cold War. The Na'kuhl agent Vosk was able to alter history starting in 1916, when future Russian leader Vladimir Lenin was assassinated, which in turn prevented the Russian Revolution from taking place. As a result, by the late 1930s Russia was in disarray and Hitler was able to concentrate on western Europe, conquering not only France, but Great Britain as well. Hitler was then able to turn his attention to the United States, conquering the eastern coast of North America—including Washington, DC and New York City. With the assistance of temporal agent Daniels, the crew of the Enterprise (NX-01) was able to defeat Vosk and destroy the Na'kuhl temporal conduit, thus restoring the timeline. (ENT episodes: "Zero Hour", "Storm Front")
Another alternate timeline was created when suffering from an accidental cordrazine overdose, Dr. McCoy entered the Guardian of Forever, and wound up in 1930s Earth. While there, he saved a woman named Edith Keeler from a traffic accident. Keeler would become a renowned pacifist whose efforts delayed the entry of the United States into World War II. Without US involvement, Hitler's government had time to complete the heavy water experiments and missile tests, winning the race to develop nuclear weapons. With such advantages, Hitler was able to win the war, and as a result the United Federation of Planets was never formed. Fortunately, Captain James T. Kirk and Mr. Spock had followed McCoy back in time, and were able to prevent McCoy from saving Keeler's life. When Keeler died, the timeline was restored to normal. (TOS episode & novelization: The City on the Edge of Forever)
|Nazis in Hitler's Germany||Hermann Göring • Grün • Adolf Hitler • Josef Mengele • unnamed Humans|
|Vosk's Na'kuhl Nazis||Ghrath • Kraul • Vosk • unnamed Na'kuhl|
|Ekosian Nazis||Daras • Eneg • John Gill • Melakon • unnamed Ekosians|
|Hirogen Nazis||Karr • Turanj • unnamed Hirogen|