There was an earth changing event that turned everything savage. A lone settlement called Pristinum exists that promises hope, but is actually a death trap to keep the city alive. The PLF are responsible, but their actions are for survival, and are made easier due to a prejudice towards mutants or helpers of mutated (more on that later) This is the short version of the setting, if you want the longer version, just ask and i will put it into another post! The plot follows the PLF, starting with the main character (lets call him Blue for now) in boot camp as a child, giving plot points and explainations. Then it progresses when the squad is in their thirties, on a mission. Their commander, Lt. Sage, gets shot and killed by a renegade in the settlement they were liberating. A small firefight erupts, showing their efficiency and showing the characters in combat. They go back to Pristinum with the body of their comrade, and are almost immediately shown his successor; Lt. Stolt. He is a complete contrast to Sage, a cold and almost sadistic soldier. Tensions flare almost immediately, nearly starting a full brawl. Night Passes. Blue and his squad are awakened to liberate another roving "wagon train" (a way of travel instituted by forsaken, which involves chaining together the wreckages of cars and storing their belongings in them) and march out to intercept and rob it. Along the way, Stolt seems to act strange, almost psycotic happy, and all of a sudden shoots one of Blues squadmates; killing him instantly. Blue kills Stolt almost immediately after, inciting the rage of Pristinum High Command. They see Blue "murdering his commanding officer" and declare him and his team enemies of the civilized world. Immediately, they send several task forces to kill Blues squad. A battle ensues in the wreckage on an old building, with Blue and his men retreating into the forest for a better advantage. Now beyond this point, I only have the very skeleton of an idea on how to proceed and would very much enjoy compliments, critism, or maybe some questions on what to do or where to go. Oh, and theres a plot twist that might explain some things which I will put in this post when I find out how to make *spoiler* font.
A story concept means nothing. I can tell you now, it has been done before. What matters is how you write it, the characterization, the flow, the imagery, all of it. There's no benefit in asking what other people think of the concept! They'll either say,"Sounds great," or, "it sounds like a ripoff of..." If the idea stirs you, write it. Then ask people what they think of the final story. After they tell you what they don't like about it, revise it, usually several times, until you're happy with it or until you throw up your hands and say the hell with it. Please read this thread about What is Plot Creation and Development?