Your heart wouldn't bleed so much if your mind was amenable to the actual lessons of history.
The extent to which you may perceive it to do so in this context might be seen to be down to you alone to decide; that to which you may or may not believe my mind to be amenable is likewise, for what that may or may not be worth...
Human nature is unchanging throughout history.
If so (and I'm not saying that it is), is that your fault or mine or anyone else's in particular?...
r The President of the USA has a duty to serve the self interest of the American people. The president of Russia has a duty to serve the self interest of the Russian people. It is not sensible, and certainly not virtuous for the President of the United States to do what is in the interest of the Russian people, unless these interests happen to overlap. This is why the UN sits with its arms crossed whilst Rwandands and Congolese butcher eachother and why countries have to sometimes form alliances and sometimes take ideological and military stands against eachother.
OK, so we each agree that the UN is far from perfect. The activitites of presidents of certain countries in serving - or attempting to serve or trying to be seen to serve (take your pick) - the best interests of their own electorates / subjects need not of itself presume the need to succeed in war against other countries in order to achive the avowedly desired effect...
It so happens that free and democratic nations tend to get along a lot better than unfree and undemocratic nations. These principles are worth fighting for and worth dying for given the right circumstances.
But, with respect, that is arguably not quite the point. Our sadly increasing experience of global war-mongering and its consequences should surely by now have taught us all that sending the troops out with some kind of agenda to "defend" something or other, whatever it may be, is likely to be fraught with possibly insuperable difficulties and bring about substantial human casualties and increased sens of enmity on all sides without necessarily achieveing the purportedly desired - or indeed any worthwhile - result; one has only to consider what is and has been going on in Iraq, Afghanistan, Somalia, Sudan and the Congo over the past three or more decades to realise that.
Best,
Alistair