Random
Step one, replace soldiers with robots
Step two, make sure all countries replace soldiers with robots
Step three, create designated war arenas in unpopulated areas
Step four, realise that this can be all done in software
Step five, ban real life wars and only allow conflicts to be resolved online
Step six, realise that all this tech can be replaced by weighted random number generator that tells who won the conflict
Step seven, create a marketplace for weights.