Daniel Kahneman and Jonathan Renshon argue we are too quick to pick a fight:
Social and cognitive psychologists have identified a number of predictable errors (psychologists call them biases) in the ways that humans judge situations and evaluate risks. Biases have been documented both in the laboratory and in the real world, mostly in situations that have no connection to international politics. For example, people are prone to exaggerating their strengths: About 80 percent of us believe that our driving skills are better than average. In situations of potential conflict, the same optimistic bias makes politicians and generals receptive to advisors who offer highly favorable estimates of the outcomes of war. Such a predisposition, often shared by leaders on both sides of a conflict, is likely to produce a disaster. And this is not an isolated example.
In fact, when we constructed a list of the biases uncovered in 40 years of psychological research, we were startled by what we found: All the biases in our list favor hawks. These psychological impulses–only a few of which we discuss here–incline national leaders to exaggerate the evil intentions of adversaries, to misjudge how adversaries perceive them, to be overly sanguine when hostilities start, and overly reluctant to make necessary concessions in negotiations. In short, these biases have the effect of making wars more likely to begin and more difficult to end.
Since the first-best, optimal number of wars is zero, this is correct. The more difficult and also more important question is whether "the good guys" fight too many or too few wars, given this strong martial propensity of "the bad guys," and treating the bad guys as the first movers. Another bias is that some "just wars" (but can they succeed?) remain unfought, usually when we do not care much about the slaughter of "out-group innocents," as evidenced by Timor, Rwanda, Darfur, etc. The U.S. entered World War II too late rather than too early, and did too little to limit the Holocaust.
Of course we need to adjust any estimate by the probability that we are sometimes "the bad guys" rather than "the good guys."
Comments are open, but the discussion will be better if we consider the biases rather than debating the merits of particular wars.