(Generous) 7 - A piece of transparent agitprop of great historical significance and, surprisingly enough, humor. I believe this humor and the tonal shifts it helps induce play a key part in retaining some of this film's power, even after seven decades. As a short film, it's pretty good; as propaganda, it's extraordinary.
I watched some WWII propaganda movies at college (from USA, USSR and Nazi Germany) and I remember them being all appalling. The enemies being portrayed as mice and other repulsive animals to be exterminated. One, from US, had the effort of building guns to kill germans (from collecting scrap metal to making cannons and ammunition) and ended with "have you killed a german today?" But this one actually is quite good.