As World War II progressed, it was obvious the Allies were going to be defeated. The Axis had been establishing their technological superiority at every turn, Great Britain was occupied by the German forces, and Stalin had been assassinated by German spies. The Soviet Union was broken, it's people scattered and turned into slaves by the tyrannical Führer's orders. The Japanese Empire, having suceeded in it's conquest of the Pacific, now moved it's fleets closer and closer to America itself. As the last Allied nation remaining, it was up to the US to fight, Fight for freedom before surrendering to opression. The joint japanese and german attack on America was brutal and efficient. Most coastal defenses were easily destroyed and, before most people even noticed it, the war was already lost.
But, hope always remains. For a few brave people survived, daring to live for freedom, even under the combined oppression of the Reich and the Japanese Empire. Those few people would keep on preparing, preparing for when they would retake their lands. It was so that, in the mid 50s, news reached the Resistance. News of a Nazi weapon that would ensure the Reich would reign supreme for more than a thousand years. A time machine. A device that could supress a rebellion before it even began. If the world was to ever know freedom, such a machine should never be used by the nazis.
it was a costly operation, but the Resistance had no choice. I must spare you here of the details, but, after many sacrifices, the Resistance seized the schematics for this "Time machine". Some sought to destroy them, but a young scientist saw it's potentials. he made a copy of the schematics, and worked tirelessly day and night in secret. Moving around, on the run from both the opressors and his fellow resistance fighters who believed that machine would doom us all.
Finally, it was done. It was but a simple machine on the outside, and there was no knowing what would happen to one who used it. The young man gathered all his courage. This was something worth risking his life for. If he failed, the world would continue being opressed forever. The Resistance would never defeat the Reich. But this... This was the single hope for mankind's freedom. With a deep breath, he took a step inside the machine, carrying with him all his knowledges and schematics of his timeline's weapons of war.
As he opened his eyes, he saw himself on a familiar place. It was his beloved hometown, once so beautiful, but now destroyed by nazi opression. That man that walked over there with a baby on his arms... Why did it resemble his father so much? The young man ran through the streets, snatching a newspaper from a nearby seller, barely able to contain his happiness. The year was 1931. The war had yet to start. This was his chance. He had a single chance to correct that which went wrong. With his knowledge from the future, he would change the course of the upcoming war.
Through many troubles which I'll spare you, he reached the US Army and convinced it's high command to give him a chance. His knowledge helped the US beyond words could permit. Some schemati the young man drew ended up being stolen, and were years later found to be in the possession of communists, but that was a small price to pay for the advantages that single young man brought to the war effort.
With his knowledges, US and USSR technology were years ahead of their time. They could work on german technology before the technology was even invented in Germany. They could throw planes that would be invented only years after in the war to aid them. And thus, the German war effort of Me 262s was utterly crushed by Sabres. Freedom was achieved thanks to the brave acts of those brave people who dared to defy tiranny even at the risk of their lives.