After a War

There is a sub-genre of fiction (detective fiction usually) which is set in the aftermath of a war. A nonexhaustive list of this includes films such as The Third Man, Three Kings, The Good German, and books such as Tokyo Year Zero (which is execrable - I feel duty bound to warn you not to read it if you're considering it), the De Luca trilogy, the Bernie Gunther series, and I suppose A Song of Ice and Fire and those Steven Erikson books if you want to stretch things a little.

As a setting for fiction that kind of background works, because everything is up for grabs. The normal rules don't apply. Somebody has taken society in both hands and shaken it to pieces like an Etch-a-Sketch drawing and now the constituent pixels are trying to find their way together again. The out-and-out chaos and totality of conflict itself has passed, but events take place against an unsettled backdrop which is intrinsically interesting as a result. It's plausible that people are going missing, settling scores, stealing things, breaking up or getting back together, and all the other stuff of good fiction, in large quantities.

A post-war environment also makes great campaign setting material for similar reasons. Red dragons have just swept through the land burning random settlements on their way somewhere else. Gibberlings have just invaded and fucked everyone over before throwing themselves into the sea en masse. A devastating plague of russet mold which almost emptied the land has just receded. The storm giant overlords have recently been overthrown and the men of Fantasyworldland have thrown off their shackles. And so on and so forth. In that kind of setting, the sandbox almost creates itself: everywhere they look, there's a plot hook for the PCs to get involved in or just a ruin to loot or explore.