"Russia" that got invaded was in fact Soviet Union and many nations of Soviet Union did not think that Germans were invaders. Moreover in 1941 until German changed thier policies they were welcomed by Russian, Belorussian and Ukrainian peasants as liberators. I don't know about Belorussia and Russia but on the Ukraine territory if captured Red Army soldiers was able to prove he is Ukrainian either by speaking Ukrainian or with help of relatives he got released immediately. In 1941 most regular folks of Soviet Union (especially from rural areas) had enough of Red terror and by that time Germans did nothing wrong, so who was the enemy for them? What to fight for? For those bastards that were terrorizing citizens of their own country? I've been studying WW2 for nearly 20 years, not including my teenage years when I had numerous opportunities to speak to veterans and regular folks who survived the WW2. My two grandfathers were veterans of WW2. And after all I saw, after all conversations I had, after all documents and books and numbers I say the terror was the way to run the state and run the army. Quoting Trotsky "…red army soldier has to be presented with choice of either honourable death in the fight or or inevitable and shameful death by firing squad.." and thus famous Order #227. Everyone's entitled to his own's opinion but opinions don't change the facts.
You also wrong in your opinion that executions were not commenced in front of the troops. There are numerous proves to that.
Now, also you statement "The only Soviet soldiers who were sent into combat unarmed were the poor bastards sent to the penal battalions" is not correct. I don't have time to present enormous amounts of memoirs and facts and systematizing them and I'm not even sure they were translated into English, but practice of sending poorly armed or unarmed units into the fight were traced until the 1944. Here's one typical story, I'll Google-translate it for you. This is the typical story of most guys that were "liberated from evil Nazis" and immediately thrown into battle. And I saw enough names on my village cemetery epitaph and I heard personal stories like this many times to know it's true.
"When the village was "liberated", all men between 16 and 60 years - all that were barely able to walk, deaf or blind - no matter - were taken into the army. We were "armed" - given half-brick and - "go, atone blood guilt" because we were in the occupied territory. We were said "you throw bricks, and the Germans may think that it grenades!". They put us about 500 souls on ice reservoir, on the opposite side - a complex building, Germans knocked in the wall slits. The wall - height of three meters. Try and climb on it if you can make through the ice. The Germans hit us with intensive fire. We could not get back - there were SMERSH (my comment - I think old man mistaken in the unit name, as normally SMERSH was not involved into such things) aiming at our backs with machine guns ... I remember I was trying to hide behind bodies of men killed on the ice and I was pushed back along with bodies on the slippery ice as machine gun fire was so intense so it was pushing bodies back. Mine detonated and then I did't remember anything... When I woke up, I found somebody picked me up and brought to hospital and this half-brick was still in my hand, it got frozen to palm. My legs were frost bitten too. I, like a true soldier, did not leave "weapon" on the battlefield (laughs). The boys said that out of 500 souls, only 15 survived..."
As I said I don't have much time to elaborate and my quick searchex did not bring up anything on this subject in English, but this topic was discussed on historical forums and some documentaries exist in Ukrainian and Russian languages.
Unfortunately there are still tons of documents that are considered as "secret" by Russian government. Especially in such sensitive areas like mass repressions etc. I had been working with documents from different sources and nobody's perfect, but only Soviets were "smart" enough with documents to present killed civilians in the battles to pump up the numbers of killed enemies and stupid enough to report much lower numbers of captured weapon... with proportions sometimes 20 dead enemies to 1 captured rifle. That is not about German soldiers, that's another conflict, but it gives the idea of my trust into single document. As I said - only complex analysis of many documents and evidences and memoirs could help there.