To be specific, war is a vortex of destruction that sucks in human beings, territory, and material, until it burns itself out. Or a paired set of mutally-reinforcing vortices.
Conflict is a pervasive part of human existence, but only some of the time does it rise to the level of armed conflict. Just as we always have weather, but only under certain conditions does it self-organize into immensely destructive hurricanes and tornadoes.
At a sufficient remove, war just seems like something that happens. Sure, human agency is involved -- we woudn't be in Iraq if not for Bush and his cabal; we wouldn't have had WWII without Hitler -- but pull back for a long view and the leaders don't seem to matter that much, most of the time. WWI just seemed to happen because there were armed states waiting for an excuse to fight; ethnic conflicts have their own inescapable dynamics.
I've had a long-standing interest in the dynamics of conflict, but I can't say I have had any great insights into it since this, other than realizing that there is a reasonably good term for the main phenonmenon that catches my attention: polarization. The way to get rid of war is to subvert the human tendency to form conflicting groups. Don't ask me how that's supposed to be accomplished, but people try.
Anyway, just taking a moment this Memorial Day to remember all of those who have been sucked in and chewed up by this process: military and civilian, aggressor and defender, guilty and innocent.