Dead Snow

I've reviewed movies about Nazi Zombies before - the ill conceived "Shock Waves", and "War of the Dead" come to mind, so it's not like it's a new concept (even Zombie Lake used the idea.)   It's an idea that you would think would have wild success.  Just mention the ideas of Nazis and zombies in the same sentence and you pique the interest of a lot of horror fans.  So, if this is such a great combination of two gruesome archetypes, why did it take until 2009's Død snø (aka Dead Snow) to make a film utilizing Nazi Zombies to this degree of goodness?