From GameGirlAdvance:
"The interesting thing about war games is that the default state of a
war game is peace. Think about it: what if you started up a multiplayer
game of WarCraft III and none of the players built
anything but workers and buildings? The natural state of the world is
for the races of WarCraft to peacefully coexist (although you would
eventually run out of resources), and this tranquility is shattered by
player actions.So the way you make a peace game is to create a world where the
default state is conflict, and the player must act to calm the violence
through a variety of means. That’s the trick: you’ve got to show peace
as something that’s challenging to achieve, not a default state."
I’m currently reading "The Shield of Achilles" by Phillip Bobbit, which certainly underlines that last sentence of the quote.
Petafloptimism 
One classic disruptive approach is the deus ex machina: the natural disasters in SimCity, and even the pixellated yellow floods in the BBC Micro’s ‘Kingdom’. If you present an world in which you’re in conflict with a nature that’s unpredictable and intractable, then there’s an easier progression to imagining a ‘manageable’ human conflict.
it isn’t about default states, it is about goals.
Who gives a fuck about computer games? If peace matters to you, get your eyes off that fucking screen.