WHY would Koverchenko do that?
At the end of the movie, why would Koverchenko want the mujas to let Daskal go? As soon as he made it back into the USSR, Daskal would've done everything in his power to make Koverchenko's life a living hell, and probably would've gotten him sent to the Gulags for being a traitor. The other two tankers would've probably held their tongues, but Daskal seems like the kind of guy who would murder Koverchenko if he couldn't get the Red Army to do it for him.
And why would the Taj grant Nanawatei to tankers who are not even asking for it for themselves? They didn't kill Koverchenko immediately because he begged for it himself, and even then they only would consider it because he they knew he was the enemy of their enemy (the tank). I mean, at the beginning of the film they murder Taj's entire extended family and nearly all his friends. How would he not still be furious with them about that? Especially the commander, the one who was truly responsible for it all.