At the eleventh hour of the eleventh day of the eleventh month of 1918, Calamity Jane fired the closing shot of the Great War. The war to end all wars, they called it. 
“I am young, I am twenty years old; yet I know nothing of life but despair, death, fear, and fatuous superficiality cast over an abyss of sorrow. I see how peoples are set against one another, and in silence, unknowingly, foolishly, obediently, innocently slay one another.”
“But now, for the first time, I see you are a man like me. I thought of your hand-grenades, of your bayonet, of your rifle; now I see your wife and your face and our fellowship. Forgive me, comrade. We always see it too late. Why do they never tell us that you are poor devils like us, that your mothers are just as anxious as ours, and that we have the same fear of death, and the same dying and the same agony–Forgive me, comrade; how could you be my enemy?”
“We are not youth any longer. We don’t want to take the world by storm. We are fleeing. We fly from ourselves. From our life. We were eighteen and had begun to love life and the world; and we had to shoot it to pieces.”
– Erich Maria Remarque, All Quiet on the Western Front
Jeremy’s note: Russian civil war, World War II, Korean war, Indochina wars, Vietnam war, Cambodian civil war, South Zaire war, Lebanese civil war, Tanker war, Gulf war, Yugoslav wars, Afghanistan war, Iraq war, NW Pakistan war, Somalia war, Libyan civil war, and the Yemini civil war just to include the ones easy-to-look-up where US troops were boots-on-the-ground. Who knows how many other conflicts the US has supported through “foreign aid” or arms transfers or other back-door methods. 
Perhaps even “tragedy” is too weak a word.