There were also NKVD combat units, most famously one which did a lot of heavy fighting in Stalingrad. (Actual desperate fighting against Germans, not the scene

There were also NKVD combat units, most famously one which did a lot of heavy fighting in Stalingrad. (Actual desperate fighting against Germans, not the scene from the awful "Enemy at the Gates" where they fire on retreating Soviet troops -- that's mostly made up for the movie).