Ukraine has about a month before it runs out of artillery shells, and the U.S. Congress cannot agree to ship more. Russian opposition leader Alexei Navalny is dead. The slaughter in Gaza continues with no end in sight. The Yemeni Houthis are attacking ships in the Red Sea. The North Koreans are testing intercontinental ballistic missiles. In normal times, pessimism can look like an intellectual fad. In times like these, it becomes a starker form of realism. The post-1945 world order – written into international law, ratified by the United Nations, and kept in place by the balance of nuclear te…