Polish cavalry, the most formidable mounted military force in Europe at the time, was slaughtered by Hitler's tank divisions early in the WWII. The Soviet cavalry, on the other hand, was highly successful - the only useful cavalry of that war, and the last useful cavalry in history. How come?
The cavalry raids by the Russians were succesfull because German military was snowed-in, frozen, hungry and sick. German rifles, cannons and tanks, unlike Russian, were not designed to be used at 20 degrees below freezing: the firing mechanisms froze, leaving German soldiers incapable of defending themselves against sudden attacks by the cavalry.
Hitler repeated history: like Napoleon 130 years before, he got stuck deep inside Russian territory in the middle of the winter. The fact that Hitler attacked in winter gave the Red Army an initial advantage. Did that initial advantage change the final outcome of the war? Maybe, maybe not. Perhaps it made the war shorter. It certainly helped Russians lose 27 million people instead of much more.
Despite attrocities that the Red Army commited in Ukraine, Baltic states and other places, its participation in the WWII was critical to the final outcome, winter or no winter. Without the Red Army, we would all speak German right now.
Why did Hitler attack in winter? Some historians say (and others vehemently dispute it) that he was delayed by the intervention in Yugoslavia. Yugoslav prime minister signed the Pact with Hitler, but the people rose in protest on March 27, 1941. Hitler was allegedly so mad, he sent 32 divisions to the Balkans to punish them, starting on April 6, 1941. Those divisions got stuck in the mountains of Bosnia, where attacks of local partisans slowly chipped at them over the next four years.
If this theory is true, and Hitler delayed attack on USSR because his troups were bogged down in the Balkans, and this delay resulted in initial losses in Russia, and this led to an overall loss in the War, then Yugoslavs can claim, as many do, that their contribution to the final victory was out of proportion with the size of the country.
Every country claims its contribution was crucial to the final victory: French resistance, Norwegian resistance, Dutch resistance, Yugoslav partisans, Red Army, British RAF and many others all claim they "won the war". Of course, each contribution was important. Each resistance movement saved some Jews, killed some Nazis, got some SS units stuck locally instead of them being available for fighting elsewhere, etc. The collective effort won the war in the end. The Axis troups were made too busy in too many places to be as effective as Hitler (and Mussolini etc.) hoped for. The question is: how would the war go if any one of those forces was missing?
Resistance in some countries, though helpful, was obviously not critical for the final outcome. Without them, war would still be won in 1945. Some cases, like that of Yugoslavia, are still hotly contested. Nobody seriously questions the critical roles of the RAF and the Red Army.
But how about the American contribution? Most Americans, just like all the others, believe that the their military - the US military - won the WWII, perhaps with a little help from "its allies". But is that true?
Surely, US military made large sacrifices and big contributions to the overall war effort, but was that effort critical to the final outcome? Most Americans would say Yes, as that is how history is taught in schools. People in all other countries would say No. Why? What is the reasoning? What would they say if asked why was American contribution not critical?
They would say that "Americans did too little too late". They would say that Japan was far smaller and weaker opponent than Germany and Italy and that it was crumbling under its own weight as it spread itself thinly across Asia, becoming increasingly vulnerable to attacks by local resistance fighters. Once Germany and Italy were defeated, the thinking goes, Japan would have surrendered even if nobody ever fired a single shot at them throughout the war, i.e., they could have been completely ignored and they would still be defeated by the loss of their more powerful allies combined with their thin spread over the Pacific.
Furthermore, America's obsession with Japan, a minor player, prevented the USA for coming and helping in Europe, where the real fighting was going on, until too many people have died. Refusing to allow docking of ships with Jews (the ships returned to Europe and all the people on board were killed by Nazis) is another qualm Europeans have with the USA.
They would also say that the African front was not critical for final victory - yet another peripheral war theater that could have been ignored with no consequences to the final outcome. Finally, many are resentful of General Patton coming at the very end, once most of Europe was already liberated by Russians or locals, riding straight to Berlin and declaring that he and his troops liberated Europe. They would say that is typical American haughtiness. Now, don't get me wrong, they appreciate what Americans did, but complain that the STORY Americans tell about it is incorrect, i.e., that American contribution, though valuable, was not critical to the final outcome. This view is not something you will hear discussed in the US schools, or US media. Who knows what the real truth is?