The soviets did take horrific losses in 1941. But here's the thing, so did the Germans. Look at German casualty reports, aside from Jan 1943 (Stalingrad), the summer months represent the costliest months of the war for the Germans as well, until summer 44 when they are fighting on both fronts.
There are relative degrees of costliness. The Soviet losses were far worse. This is what I said "If you extrapolated that trend you would not extrapolate it to Soviet victory, you'd extrapolate it to exhaustion of Soviet manpower and industry". The rate things were going in '41, the Soviets would bleed to death first.
My point was not that the Germans had proven that they could win in 41. My point is that if things had continued in the manner as 41, the Soviets would have certainly been exhausted first.
Germany is grossly over extended with logistical issues and an army that is slowly bleeding out. You can even transfer half of the manpower involved in occupational duties as highly unrealistic as that would be, and it wouldn't have made a difference in 1941. If it doesn't make a difference in 1941, it doesn't make a difference in '42 or '43 or 44' or '45.
Germany continued to inflict disproportionate losses on the Soviets in '42 and 43. The Soviets didn't achieve parity until well into 45.
I'll ask again. How does Germany plausibly win. Plenty of people have said Germany would have won, but when questioned they don't provide a reason, they just say "Because" or get nasty!
I already gave you a reason, attrition. I'd hardly say it was an inevitability but it certainly was a possibility.
The Germans inflicted 3-1 and 2-1 loss ratios on the Soviets well after the tide had turned. The tide had turned because everyone could plainly see that the Soviets were going to outlast the Germans. But the Soviets were going to outlast the Germans with western support. Without western support that doesn't seem so inevitable.
The German economy would much outpaced the Soviet one. Historically the German economy grew but was inhibited by bombing and the oil shortages. Without the western front the germans wouldn't be using oil on planes and submarines in the west and would have faced no bombing at all. Historically the Soviet economy fell a lot during the german invasion then recovered to about 80% of pre-war levels or 90% if you include imports as part of the economy. The Soviets made up for their relative economic decline by vastly increasing their mobilization of the economy. Imports helped with this substantially. Between 42 and 44, the soviet military expenditures rose from about 100 billion to 125 billion rubles. Imports in 44 were about 25 billion rubles. Naturally Soviet military expenditures probably would have risen without imports but imports were a very, very key part of the rise.
So if we assume no western front then Germany with it's additional resources could have plausibly just continued to trade territory with the Soviets on Soviet ground in '43 to '45. They dont suffer the summer collapse in '44 because they have the resources to supply those armies. The soviets have significantly less materials for their offenses. Suppose both sides took losses at their historical rate, that is to say that the Soviets gradually shift from losing men and material about 3-1 to about 2-1. That is to say we are supposing the Soviets improve their ratio as they did historically despite the fact that the Soviet material position is weaker.
Now the obvious retort is that in 45 the Germans run out of men and they can't just strip the garrisons in France least they face a revolt. Well, let's just consider the casualties on the western front and the loss of Italy. Without the invasion of Italy there would be no surrender of Italy meaning that Italian troops could have continued to serve garrison and combat duties. Even though the Italian army hardly came across as a juggernaut, you are talking about 4 million men in uniform, some of them were quite useful. And the casualties on the western front account for another 800,000 fighting men that were not available.
So now lets imagine the Soviet offensives of 44-45 again but with these new conditions. The Soviets attack the Germans, this time in the summer. They're driven back once again and they're forced to commit another million men... because they've actually got those million men to commit thanks to the lack of a western front. There's 600k Germans who weren't casualties in the west, 200k Italians who weren't casualties, 130k Germans who aren't needed to defend Italy and aren't needed for garrison duty in territory of their ally, well that's only 930k men but still, that's a pretty useful number. So the Germans are holding things together without desperately stripping the french or Norwegian garrisons.
And at this point the Russians are in a bind. They have mobilized completely. This has let them keep a 6 million man army in the field but they dont have another 6 million men after that. They've taken far more losses then the Axis. The Germans have heavily mobilized but can go a little bit and history shows they would be willing to. The soviets are already at total war, they've been devoting everything they can since 42. Anyone can see that time is on the germans side in these conditions. If there's another year of brutal warfare the germans will scrape the bottom of the barrel and fight on while the soviets have already scraped the bottom of the barrel. It's easier for the Germans to make their factories give up 1 million men then for the Soviets to find yet another 2 million men to spare in their factories. Then on top of everything the famine or '46 and '47 rears it's ugly head.
I'm not going to predict the outcome, there's simply too many different things that could happen, some resulting in Soviet survival, some not. But it's very clear that the Soviets would face an existential threat at this point. The Germans would be exhausted but not facing an existential threat. Historically, the Soviets could keep fighting on in 45 because they knew they were going to win and could see things improving every year. But without that certainty they were going to win and with things not getting better year after year it wouldn't have been so certain they would have survived so much.
Looking at things very broadly, it's not a very complicated idea. It's common knowledge that the Soviet commitment to the war was overwhelming. They didn't hold back but it was still a long, hard fight and required every bit of manpower they had. We are now going to suppose that they dont have some of the resources they had historically. Naturally that is going to mean a harder fight and require even more manpower. That's additional manpower they didn't have.
Now I'm sure that you are going to say that this assumption or that one is unrealistic. I'd agree, I hardly think the Soviets or German would have followed their historical strategy if there was no western front. I'm just trying to show a baseline that's within the realm of historical plausibility. It may be true that Hitler sealed his fate in '42, that's too complicated a question for me. But I think it's very much clear that the Soviet Union completely on its own was not certain to win. Even though the eastern contribution was greater then the western the western was still very important because when things are close to balanced, a relatively small contribution can tip the balance very greatly. Suppose the soviets had another 3 years to industrialize before the war. That would have greatly helped their chances but would have done so through a relatively incremental increase in economic output.
