According to data in the book by Francis Beer, “Peace Against War”, the following trends can be observed over historical time: wars have been getting

• more severe (i.e. more battle deaths)
• shorter in duration
• more extensive (more countries involved)
• about equally frequent in war starts.

The greater severity and shorter duration can be explained by the invention of more deadly weapons. The greater extension is probably due to the existence of more countries that are in contact. The unchanged frequency of war starts says something about the human propensity to escalate conflicts into wars.

We can diagram the changes as indicated below. In the past, wars were longer but milder, as shown by the humps, and peace periods between wars were shorter. The tendency now is toward sharper but narrower peaks of war, with longer periods of peace in between. (This is a rather idealized picture, since the real occurrences of war are much less regular.)

What of the future? The trends bifurcate: either the peaks become so high in severity that wars will annihilate civilization or even humanity altogether, or they become so narrow that wars will disappear and there will be perpetual peace. (The alternative between nuclear annihilation and perpetual peace is often put that way qualitatively, but the numerical trends tend to confirm it.)

Which will happen sooner: the heightening or the narrowing of the peaks? One could attempt a quantitative assessment, but the data are probably not good enough to be able to predict. And perhaps human decisions will intervene, one way or the other.