Ok, since it is not specifically in germany, now that there is no nazi in the title, you could do this. Well, you could base it in japan. The plot would start out with Paul Tibbets (or a generic character, doesn't matter much) dropping the bomb on japan.
So, this is in a cutscene first, then, it hits. The camera lowers to look down from a top down view. Next thing you know, chaos is ensuing, and this bomb, is slowly moving outward from the impact area. The camera lowers and centers, looking on to the destruction. You see footfalls all of a sudden landing in front of the camera.You see them as they make it to their destination, a bomb shelter. Exactly 17 people make it in. The camera then cuts to inside the shelter. There is total disorder ensuing. Everyone of these 17 people are yelling about how they wonder what happened to their families, their friends, etc. They then, after the shrieks of the bombs, and unfortunates that were trapped outside stop, they devise a plan to go out, in a set of units, as now, they have to scavenge as much as they can of supplies before they start hiking out of the city(Hiroshima). Well, this goes, obviously as bad as it could. So, they all split off into groups of four. Well, there is now 4 groups of four. That leaves one person, the person the player picked before the game ever started. They call s/he their "scout". Now, the game goes over to the player. The player starts in the shelter. They then get an objective: Get to the market. So, the player goes there, it is a fairly placid experience, as they are unarmed. They get to the market, only to find a staggering individual. A cutscene triggers here. This creature is quite fast, yet unstable. Player steps on a shard of shattered glass, and alerts the thing. It turns, only to reveal it's hideous visage to the player in a Resident Evil like fashion, to harken back. It then screeches, then starts running to the player similar to that of the bomb zombies in the first game. It attacks the player; scratches the player's face. Player then has to run away from the zombie, to the shelter. If you are interested in my idea so far, then say so! I would love feedback from the developers of the most well made zombie game I've personally played. If you say you like it, then I will post some more of my idea. Thank you for reading, as to have been reading this, you had to have read the script.