The Nazi zombies in this film are a combination of typical zombies in popular culture and ancient Norse mythical beings known as draug. A draug is a undead being who would (like a vampire) inhabit graves. They would often out of jealously live in the graves of important men as they often had treasures in them and protect these treasures as if they were their own.
This film's main trailer shows black-and-white World War II archive footage including battleships, parachuting and a command room featuring Adolf Hitler but this material is not seen in the actual movie.
The trivia items below may give away important plot points.
The character of Erlend wears a t-shirt prominently featuring the words "Brain Dead" in English. Erlend's demise at the hands of a zombie is exactly the same as the first zombie kill in the low-budget New Zealand film Brain Dead (2007)--the zombie gouges the victim's eyes and splits the skull in half.