The Soviet Union played the most decisive role in the defeat of Nazi Germany in WW2

"D-Day; The Allies used a total of about 160, 000 soldiers, losing over 12, 000 while destroying only 4,000-9,000 Germans. This is not a good ratio (for Allies)"Agreed, it is not a good ratio. However, the USSR often suffered much worse ratios against the Germans in larger battles for all of 1941, and many large battles in 1942. This is part of how the USSR came to lose a total over 27 million people in WWII. Not About D-dayThe US/UK war against Germany should not be thought of in terms of D-day. Because it would be a requirement that Germany was strategically defeated before a D-day date would ever be set. Just as Germany was so defeated strategically when D-day happened in 1944; at that point it was clearly something of an inevitability. Similarly, Japan was strategically defeated before the theortical invasion of mainland Japan, Operation Overlord, that never occured. This is common US strategy. The US/Uk would invade places like N. Africa, Italy, the Balkans, Denmark, and Norway to weaken Germany before a major invasion of France and continental Europe. They would also wage a very intensive and destrucive bombing campaign to cripple german Industry, and wipe out the German airforce. The allies, with control of the sea, can threaten every border and outpost of Nazi Germany along the coast. If Germany defended france too much, the allies can take advantage by attacking a different place like Italy or the Balkans. The German army would be forced to be disperesed by such tactics, or focus in one place and be easier to surround. Therefore, Germany would not be at full strength in Europe during D-day, but would have suffered many years of strategic bombing campaigns and fighting battles on the peripheries of the Nazi German empire. The US would not rush into a big land war against a prepared Germany in France. Example, German defenses against D-day were very spread out across the entire coast of France, Belgium, NE, and northern germany. While the amphibious invasion can concentrate its forces and fire power, the defenders will be spread out over a large area. Also, with control of the skies the US/UK was at liberty to bomb bridges, logisitical targets, and german reinforcements as part of the invasion. They also drop paratroopers to further block German reinforcrements. Given the overwhelming advantage of initivative in such an invasion, and the heavy dominance in air and naval superiority the allies enjoyed, such an invasion would be a realistic possibility even without the eastern front of WWII. Also, the US would not have to fight all the way from the middle of poland to moscow, then all way back to Berlin like the USSR to win. But Just from Normandy to Hamburg, since Germany was much more willing to surrender and negotiate with the western allies. There is also the real possibilty the US would still have invented the atomic bomb in 1945 and forced a german surrender then. "I have different information from a book called "The Russian Century" by Brian Moynahan. It states that Russians killed 7 times as many Germans as the Allies, another fact saying that 10 times more Germans surrendered to Allies as Russia."Perhaps, I don't know how that book counts different categories. I used figures from wikipedia that come from the German HighCommands WWII sources for German soldiers KIA. Figures show 8 million Germans did surrender to the US alone. Overall the US captured far more Germans than it killed in all theatres it fought, including N. Africa. Utimately, the US also killed more Germans than Germans killed americans. The same is not true for Germans vs Ussr. if 45% of Germany's losses were inflicted by non-Russian forces, then that can also be accounted for the difference in amount of German machinery operating on the Western vs. Eastern front. German tanks, artillery and Luftwaffe played an enormous role in their success"True, but then why don't we need to account for all the German tanks, artillery, and planes that were NEVER built because the UK and US bombed the factories that built them? Or bombed resources or railways necessary in their production? US and UK navy also denied Gemrany resources from places like Norway and N. Africa over water. The US would try and defeat the luftwaffe far before it engaged in a full land war, and the US probably could have certainly done this since it produced many many more planes than the Germans. German units on the western fronts would often only move at night because western allied air superiroty was so strong and such a threat. US aircraft production was so much higher than Germany's, and got good ratios, that it was destined to win the air war eventually. German blitzkrieg with tanks relied on massed and concertated assaults with said tanks. These large grouping of tanks would have been very vulnerable to allied air power. German blitzkrieg tactics wtihout air superiorty would have been much less effective against the US than against Russia. And without stukas for support would not have been as effective on the ground. Also, the western front terrain was not as favorable to blitzkrieg tactics as the flat open steppes of Russia. Luftwaffe was defeated mostly by non-sovietsThis point means alone the USSR would have faced a much stronger German airforce and suffered from stronger German air superiority and bombing, and that even without the USSR the allies would likely have been able to defeat Germany in the air. German air losses before the invasion of Russia are regularly predicted to be around or over 5,000 aricraft. (3,300 in the battle of france in britain, others in norway, balkans, and poland) http://en.wikipedia.org...(1939–1945)From June-Decemeber 1941, German lost a little over 2,000 aricraft compared to 21,000 Soviet. Such high soviet losses make allied mateiral support even more important for replacements. (same source)In 1943, 60% of German airforce was located in the west. This % would rise towards the end of 43 and be higher in 44, and then in 45. (same source)The German airforce receieved its catastrophic defeats in 44,45 against the west, because they could chase german planes into the heart of German from the UK. (once the P-51 arrived)"Japan"The US and UK agreed to a 'Germany First' strategy anyway. The reason they did so is because they did not really see Japan as such a threat. Germany would be defeated first according to US/UK strategy. http://en.wikipedia.org... There are two reasons why Japan was never a serious threat to the US. 1: Even without the USSR, most of the Japanese land army was in China busy fighitng the Chinese nationalists. The Japanese army had inferior tactics and only obselete light tanks. Realistically, it could not even threaten the US with a land war due to these facts and distance. 2: In june 1942 the Jap navy was crippled in the battle of Midway that had nothing to do with the USSR. Early on, Japan lost the potential to be offensive against the US and could only defend what it had gained up until then. Again, Allied supplies are very important here for Russia though. The US/UK also provided support to the chinese nationalist in terms of war material, tanks, and planes. Without which the Japanese could have finished subduing the Chinese who had lost 2 capitals to the Chinese already, and were forced to move to a third. The chinese communists were still a relatively minor force at this point too. Meaning, without US aid and supplies the USSR wold have most of the Japanese land army based on its Eastern border with a much weaker, or even collapsed China. It is possible Japan would have invaded, as it did in 1904 during the Russo-Jap war. The USSR could possibly face Germany, Italy, and Japan, being surrounded, and having lost its industrial heartland and several million soldiers to Germany in the very first months. WIthout allied Aid and contributions, it becomes very hard to see how the USSR might have won.