Indeed, Russia is unconquerable
Not even close to true.
Russia had no reserves left the only men not under arms were people unfit for service. They even began using women for military jobs. Russia was having a problem finding enough people for industrial and agricultural jobs. As soon as the war ended huge numbers of soldiers were released from service and sent to work because the economy was so bad. Without lend lease help they were stuck doing everything on their own, lend-lease provide large amounts of food and fuel. People always only look at military equipment that was provided and then say lend-lease wasn't significant. Ignored is that the bulk of lend-lease aid was tools, fuel, and raw materials. This was was was needed most badly and was the most significant impact from lend-lease. The aid stopped immediately at the end of the war.
The Russians were testing out wooden planes because but for the aluminum we supplied they would not have been able to build the planes they ended up building.
US and UK forces DID NOT outnumber German forces to the same ration that the Soviets outnumbered German forces. Germany devoted most airpower against the West so let the Soviets control the skies.
In the various engagements even though they had full control of the skies and outnumbered the Germans in greater ratios than the west ever did, the Soviets incurred far more casualties than the West. The West had winning casualty rate. That means the West inflicted more casualties than suffered. The Soviets had a losing rate. They suffered more casualties than they inflicted.
The West had a much larger air-force than the Soviets. The aircraft was vastly superior to Soviet aircraft. Britain and the US were developing jets during the War but the war ended before they were used in earnest. The first Soviet Jet was developed later as the result of stolen technology. The US had atomic weapons that could have been used on the USSR. It was year slater again through stolen technology the Soviets developed the bomb.
Since Soviet forces suffered substantially more casualties against outnumbered Germans lacking air support then obviously they would suffer many more casualties against a Western force larger than the German force which would have been able to establish air superiority. The ground attack aircraft the Soviet shad would have been easily shot down by Western forces and they provided a major amount of the damage against German forces.
Lendlease was responsible for 2/3 of the Soviet aviation gas supply. That cut alone would severely curtail the flying abilities of the Soviets. None of these things are ever considered.
If we fought the Soviets conventionally we would have suffered casualties to be sure but the Soviets would not have been able to prevail. They would have suffered huge losses that they would not have been able to make up because there were no men left to try drawing from.
Stalin knew this, knew about the atomic bomb and would have capitulated to Western demands rather than risk war. He knew the economic might and military might of the West and that he could not prevail. That is why he refused to officially take part in North Korea. Soviet planes that did take part had no markings. He wasn't willing to fight the West.
Operation unthinkable was simply a contingency plan. There are always military contingency plans. it was just in case war did happen with the USSR.
Hitler wasn't the idiot that people like to pretend. He became crazy at the end and was a lousy commander in that he would not allow his military commanders to do what they wanted- which is good because that would have prolonged the war. Germany could have defeated the USSR Hitler wasn't insane. If it wasn't for Lend-lease the Soviets would have to have signed a peace deal with Germany ceding a large amount of territory. But for out efforts there would have been a stalemate, the stalemate he expected the West to have with Germany and Stalin feared the West was going to steal his idea wait in the shadows and after both sides were exhausted to swoop in.
At the end of 1941 Hitler had good reason to think the War in the USSR was winding down and would soon be over with the USSR suing for peace and giving up large swaths of land. Not only were millions of Soviet forces killed or captured, the main areas of Soviet industrial might had been taken. Ukraine accounted for most of the explosives production and a land taken also accounted for a large amount of food production. Industry was in a shambles. Hitler underestimated the ability of the US to supply the Soviets so they could continue fielding a viable force. Finding more men to stick in uniform is one thing.
because so many former Soviet citizens were under German occupation they were forced to use men from the interior of the USSR as replacements.
Feeding them, providing them with equipment and ammunition was a problem. The US provided machine tools and other equipment to outfit factories beyond the reach of German forces. There was little industry in the region at the time of the German invasion were provided a lot of materials they used to rebuild industrially. The manpower to produce aluminum, steel and other metals needed for production of tanks, planes and guns would reduce the pool of men available for military service and working in factories to produce such items. The finished weapons provided were a stopgap to be used as the Allies helped the USSR to build factories. So we helped them to build factories and provided them with raw materials for those factories to use. We provided them with railroad equipment and most of the trucks they used so that they could transport materials to the forces in the field. We also accounted for 2/3 of their aviation gas and the materials used by them for ammunition. Hitler expect them to run out of ammo and have to surrender because he knocked out most of their ammunition production. He had no idea we would be both willing and able to more than make up for the loss.
Anyone who knows about military matters will tell you logistics are the key and that is what no one looks at.
But for the West the USSR would have capitulated and basically would have been an Asian power. To be sure Stalin would have spent years rebuilding to one day renew the war to try to take the lands back but it is doubtful Germany would have been able to be dislodged at that point.
The West saw such a huge Germany as a major threat so didn't let that happen and supplied the Soviets and simultaneously built up their own forces to help defeat Hitler.
On the History channel Website we had a huge debate over Unthinkable where all the forces of each side were listed and took into account atomic power and took into account the Soviet economy less lend-lease and it was quite clear that the Soviets could not go toe to toe with the West if there had been a war. Stalin never would have gone to war though the West could have gotten a much better peace deal without needing to go to war.