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 inhabit graves, often the graves of important men, as they often had treasures in them. A draug would 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.