Why is war futile?

You will gain a variety of answers to this question.  
Some will argue that it is futile because of the massive loss of life and displacement
that results from it. Even in the most compelling of wars, the amount of dead and/ or
injured, as well as the number of those who are homeless or orphaned as a result are
staggering totals.  At the same time, an argument can be made that war is futile because
it is infinitely regressive and continues on no matter what.  Wars are waged and fought
and while individuals might believe that a particular war is so bad that it "will end
all wars," another one ensues afterwards.  I would think that another reason why war is
futile would be that the people who die are usually the ones who do not wage it.  For
example, Elie Wiesel writes, "When adults wage war, children die."  In this line, there
is much there about who really suffers in wars.  The children who die did not authorize
or commission the conflict, yet these are the ones who die int he process.  This might
be another reason why war can be seen as futile.