And *cough* the engineless tanks being rolled off the production line
Engines are expensive comrade! And if we do not have engine, we do not need fuel! And if we do not have engine, we do not need driver! Or transmission! Tank cannot catch fire when Fascist Invader shoots fuel tank! Truely, engineless tank is marvel of Soviet engineering!
But Comrade Commissar, how do we move it?
PUSH HARDER DEFEATIST COWARD!In all seriousness quite a few countries did things like this. Germany had a number of surplus or salvaged tank turrets built into concrete bunkers and I read an account from the Siege of Memel that German troops were pushing a Panzer II in and out of a covered hide for a few days after its engine went out because even in late 1944, the 20mm autocannon was more than enough to stop infantry attacks.
Back on the subject we've derailed to, IIRC Germany didn't retreat through Finland and the German scorched earth policy, lets be honest, was first used by Russia. As the Axis advanced, the Soviets put things to the torch, took all war materials east, and even dismantled whole factories.
Secondly the best fortified borders as of 1939-40 was eastern France, followed by Belgium (excellent fortresses and the still-effective today "water line" of canals), followed by Czech-German border (the Sudetenland annex conquered those defenses without firing a shot), and Finland had a pretty dismal border defense with one saving grace; camoflague. The myth of Finnland having this AMAZING FORTIFICATION SYSTEM was propaganda used to cover ass after the Soviets were humilitated trying to take it. In truth they had about 14,000 cubic meters of concrete in a little over a hundred bunkers, which is about as much concrete as they put into an opera house. Unreinforced concrete, for that matter.
And lastly I think Lend-Lease and its war-winning effect can't be understated. Two-thirds of Soviet trucks were US-built, and the best in their class on the Eastern front for either side. Trucks seem like a pretty minor element until you consider that Soviet mass without maneuver is how they had pockets of 300,000 soldiers gobbled up at a time in 1941. And looking past just trucks, they had 2000 foreign-built locamotives compared to 98 domestic locomitives produced during the war. Soviet strategic and operational transport was dominated by US-produced vehicles, without which they would have been reduced to pack horses and marching as the Germans frequently were.