A tragedy of the commons is a situation where autonomous individuals all acting in their self-interest, due to these self-interested decisions that none could be expected not to make, lead to a situation that creates gain for none of them and loss for all.

War is precisely this phenomenon. In a world where war gives the victor many advantages and lets him avoid catastrophic disadvantages, any nation would be irrational not to prepare for war, be ready for it, and be willing to engage in it with every cruelty necessary to ensure success. Treaties and agreements can come to pass to mitigate things like genocide or "war crimes"--but these are generally not guaranteed and are not always abided by, especially if they ever contradict an action that can give any nation considerable military advantage. If a powerful nation does not abide by such agreements and wins the war, there is little any other can do to press war crimes charges beyond raising indignation.

But while it is in the clear self-interest of every nation to wage war, the whole world and all the nations lose incredibly more than any nation has ever gained by winning war. Nations have gained by winning this war or that, but does anybody doubt that if there were a way for the whole world to avoid war and military science forever, the whole world would not gain immeasurably? Of course there are always hypothetical "what-if" scenarios--what if the whole world were ruled by a cruel dictator, is peace good then?--and so on. But given the world as we know it and history as we know it, leaving every imaginable scenario aside, does anybody conceive that the whole world and everybody in it does not lose a great deal by there being war at all, no matter what any nation has ever gained in a given war? War is a tragedy of the commons--it is in the best interest of all nations to wage it and be ready for it, and so they will do so; and yet they all lose incredibly in this dynamic, though any individual nation would lose much more should it lay down its arms and let all the others desolate it. In this tragedy of the commons each nation has no control over any nation but itself, and if any nation simply laid down its arms and did not resist with violence, it would mean desolation. But yet when none do so and all do the opposite--equal desolation, only for the whole human race.

There are many examples of this tragedy of the commons dynamic and in many of them there is a point at which they cancel out--the value in the given self-interested action goes away when the loss to all becomes manifest, so people simply cease to do it. For example, on a given rush hour morning, a certain area of the city may be very thin in traffic. It is in the self-interest of everyone then to take that route, but when they do it becomes no longer valuable. It is now congested, and while all who have sought to gain have lost, it will not just go on getting more and more congested forever; it is no longer valuable to take that route. But with war this does not seem to be the case. When the war gets more and more brutal, each nation must get more and more brutal; the more brutal the others the more it is in the interest of each to respond in kind. The same goes for war technology. If somehow we had found a way to agree and enforce the agreement that no new war technology would be developed after, say, the Civil War era, we would have much less desolation due to war than we had in the 20th century and will probably have again. But there is no such guarantee of any agreement possible, so it is in the interest of each to develop more and more destructive weapons. If any nation decides not to do this, it can be sure the others will; and now that nation will be the one desolated. And yet if all could possibly be sure none of the others would, it would mean incredible gain for everyone. Now war technology has progressed to the point where it is possible to make humans extinct or in the least radically depopulate the Earth and wipe out all civilization. We have not done this yet with our nuclear technology, but we have not yet had it for even close to a full century. Give us a thousand years, and I'd say it is extremely unlikely that such a catastrophe will not in fact happen.