Russian soldiers say they were sent into battle with 'blocking' units behind them to stop them...

CPT Lawrence Cable the execution of retreating soldiers is true or not?

LTC (Join to see) - The scene in the movie is a fabricated event. The Soviets certainly had punitive units that rounded up who had either left their positions, been forced to retreat or simply went AWOL, but they didn't operate the way it was shown in the movie. I can't find anything that I would consider reliable that would indicate that the Russians forced units to charge in front of their own guns.
If you read "The 900 Days" on the siege of Leningrad, or 'Stalingrad, the Fateful Siege", the survivors are shown as heroic, surviving enormous hardships.
We have people that picks up stragglers and deserters too, called MP's.

CPT Lawrence Cable yes, I was trained to be that as well.

95 Bravo then 31 Alpha. I am behind the black man kneeling. I am standing almost Center behind the sign. I was 34 years old.

Yep - back to WW2 motivation techniques ... Bravery or Bullet!