Samuel Moyn : Who launched war : do laws of war impose limits how war carried out ? After WWI , aim was to end war , but in recent years , aim shifted to making it more ' humane , ' he says . Moyn : Focus now not to end enemies ' aggression , but to stop atrocity . Vietnam a low point . Since 9/11 , our wars much cleaner , lawful ; but WWI idea of ' war to end wars ' remains , he says .
Samuel Moyn : WWI launched debate : can laws of war impose limits how war carried out ? After WWI , aim was to end war , but in 100 years , aim shifted to making it more 'humane , ' he says . Moyn : Focus now not to end nations ' aggression , but to stop atrocity . Vietnam a low point . Since 9/11 , our wars much cleaner , lawful ; but WWI idea of 'war to end wars ' failed , he says .