The 2001 film Enemy at the Gates shows Soviet Red Army commissars and barrier troops using a PM M1910 alongside their own small arms to gun down the few retreating survivors of a failed charge on a German position during the Battle of Stalingrad. The film misrepresents the role of blocking detachments in the Red Army. Although there was Order No. 227 (Russian: Директива Ставки ВГК №227) that became the rallying cry of “Not a step back!” (Russian: Ни шагу назад!, romanized: Ni shagu nazad!),[36] machine gunners were not placed behind regular troops with orders to kill anyone who retreated, and they were used only for penal troops. As per Order No. 227, each detachment would have between three and five barrier squads per 200 personnel.[37][38]

If you refuse to read your own sources, I really don’t know why you bother engaging.