This is what I've got so far:
It involves 2 countries surrounded by mountains, completely cut off from the outside world.
The two countries, Piege and Links, suddenly start warring when the king of Piege (a monarchy) is assassinated. With literally one person to suspect, they attack Links (a parliament). This war results in a 50 year long stalemate, since both countries are equal in every regard, economically, militarily, and technologically. During the 30th year of the war, Piege has a sudden rush of technological innovation within the span of a month. This event, called the Divine Gift, kickstarts a program called the Peacekeeper program.
The goal of the Peacekeeper program is to create a type of soldier better than anything that Links can throw at them, and quickly end the war. Several hundred clones are engineered of a single soldier, and they are all bred to be what the government wants them to be - killing machines. But then, on the 20th birthday of the clones, when they were supposed to be deployed, both countries come to terms on a peace treaty. The Peacekeepers are dismissed and sent into the reserves, since they are technically just soldiers, but since one of the conditions of the treaty was drastic decrease in military strength on both sides, many are just discharged.
The main character, Jack, or PK71 as he is known legally, is one of the soldiers who were discharged. The story is about Jack, and coming to terms with finding new meaning in his life after being discharged, as well as uncovering the truth to every event in the past 50 years, including the start of the war and the history of both countries.