Major wars have become less frequent, but a curious feature of the wars we still observe is that almost nobody starts them. When wars occur today, they appear to start themselves, or are started by some unknown entity. I learned this from a new article by Hathaway et al. Here are selections from the abstract:
This Article is the first to examine “war manifestos,” documents that set out the legal reasons sovereigns provided for going to war from the late fifteenth through the mid-twentieth centuries. We have assembled the world’s largest collection of war manifestos—over 350—in languages as diverse as Classical Chinese, German, French, Latin, Serbo-Croatian, and Dutch...
Examining these previously ignored manifestos reveals that states exercised the right to wage war in ways that would be inconceivable today. In short, the right to intervene militarily could be asserted in any situation in which a legal right had been violated and all peaceful channels had been explored and exhausted. This Article begins by describing war manifestos. It then explores their history and evolution over the course of five centuries, explains the purposes they served for sovereigns, shows the many “just causes” they cited for war...Hathaway, Oona A. and Holste, William and Shapiro, Scott J. and Van De Velde, Jacqueline and Lachowicz, Lisa, War Manifestos (September 15, 2017). University of Chicago Law Review, Vol. 85, 2018 Forthcoming; Yale Law School, Public Law Research Paper No. 617. Available at SSRN: https://ssrn.com/abstract=3037538
Self-defense is the most popular justification for war throughout the period studied, but it's interesting that its prevalence steadily grew from the middle of the twentieth century. Most traditional justifications for warring have become obsolete. Religion was once a fairly common reason for going to war, but now explicitly religious wars among states are virtually extinct.
Don't be fooled into thinking that interstate aggression has been humanized. Quite the contrary, these data only suggest that war is an increasingly algorithmic process, increasingly devoid of human agents: When every player in the game invokes "human rights" to blame it on some other guy, this is not evidence that human rights have been normalized; it is evidence that humanity has been evacuated from the underlying process, through the cold and calculated manipulation of human emotions for ulterior purposes.