Prove Russian won the war.
I will start at the furthest extent of German advances, the high water mark of September 1942. I have highlighted the major successful allied strategic offensive operations involving the American ground forces below to easily find them. There are two German offensives here whose loss is notable as strategic gains by the allied forces.
- Start of Battle of Stalingrad (Aug 1942)
- Operation Uranus (Nov 1942) <- Encirclement of Germans at Stalingrad.
- Operation Saturn (Dec 1942) <-Destruction of German forces in the Caucus and Donbass regions.
- Start of Operation Torch (Nov 1942) <- United States first combat troops in significant numbers open new front in European Theater.
- End of Siege of Stalingrad. (Feb 1943) < - Generally regarded at the turning point in the European Theater.
- Operation Husky (July 1943) <- United States leads first major invasion into European continent since the UK evacuation of Dunkirk 3 years prior.
- Operation Zitadelle, aka Citadel (July 1943) <- Marks the beginning of the collapse of the Eastern Front. From this point onward, Germany is on the defensive. No major German operation on the Eastern front has the strategic aim to achieve victory after this point. The German defensive phase of the war begins.
- Leningrad–Novgorod Offensive (Jan 1944)
- Soviets enter Estonia (Feb 1944)
- Operation Bagration - (June 1944) <- Destruction of German Army Group Center. At its conclusion Soviets begin invasion of Germany. Romania, Latvia, Estonia and Poland are captured/"
liberated" by the Soviets as a result.
- Operation Overlord (June 1944) Western Allies finally open the long anticipated 2nd front Stalin had demanded. He will later lament the irony during the Cold War.
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Operation Northwind (December 1944) <- Last major German Offensive on Western Front. The failure here lay open the path for the allies to advance to the Rhine.
- Vistula–Oder offensive (Jan 1945) <- Soviet forces advance to 36 miles from Berlin.
- Operation Spring Awakening (March 1945) <- Last German Offensive on Eastern Front.
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(March 1945) <- Western Front breaks through Siegfried line.
- Battle for Berlin (April 1945) <- Russians begin battle for Berlin. Ends May of 1945.
From Operation Husky onward, the combined American and UK forces battled ~1/5th of the available combat forces Germany sent to the Eastern front.
From the above, I would say this evidence is contrary to your statement that the Russians merely "held the eastern Front".
As to Russian military leadership "not being there", for the period of June, 1941 - August, 1942, I would agree with you. However, I do not believe the evidence supports your statement over the period of September 1942 - May 1945, being a period of time greater than the entire period of United States direct involvement in ground campaigns in the Western Theater.
Notably there has been a interesting academic scholarship noting an inverse relationship to Stalin's and Hitler's direction in military affairs and the relative success of their militaries as a result. Summation, more interaction from the dictator equates to less success.
The allied forces were the turning point in the European front.
I agree with this statement, but presumably for different reasons than your own. Without the material support of the Western nations there is a high likelihood that the Soviets would have lacked the supplies necessary to execute large scale deep penetrating operations. Many later Soviet leaders and interestingly some Soviet scholarship would note the same.
While it is plausible to argue that the Western Allied Nations ground campaigns drew resources from the Eastern Front which in turn allowed the Soviets such successes, it is not outside the realm of possibility that the Soviets would have succeeded regardless.
Arguably the single United States service branch that contributed to both the Soviet successes and Western Allied victories and thus America's greatest service contributor to the victory in Europe was the United States Merchant Marines. Despite being the first to deploy in significant numbers into the combat zone and suffering a higher mortality rate than any service branch and without whom, neither an American or Soviet victory would have been possible. At the end of the war they received no government pensions or benefits and could not take advantage of the GI Bill.
They were the first and last service to lose service members in significant numbers to combat action beginning in 1940 and losing their last of servicemen to an enemy mine in 1947. They didn't even get a major motion picture until Tom Hanks starred in one last year.
I had to look some of the names of the operations and starting months up individually, but most of this was picked up from years of reading and following David Glantz and Jonathan M. House whom I first encountered after reading Glantz's master thesis at the Combined Arms Research Library.
A great resource that is publicly available for perusal. I strongly recommend it and not being one to horde knowledge or access to it, please find the digital version of the library here:
cgsc.contentdm.oclc.org