[Does so]

Once that is accomplished, then Commissars should be assigned to each unit to ensure no further straying.

Commissars were armed, and were to ensure Soviet troops didn't retreat. Think of Obama's "Leading from Behind"...

[rxh4n1]

That was the NKVD “blocking troops” that deployed behind the regular units. The political officers were to indoctrinate the soldiers and keep an eye on the officers.