From an essay on foreignaffairs.com by Karen Yarhi-Milo headlined “Why Smart Leaders Do Stupid Things”:

To many observers, Russia’s decision to invade Ukraine was, obviously, irrational. Ukraine is Europe’s largest country, and Russian President Vladimir Putin was short on both good troops and quality weapons. No other state (aside from Belarus) was sympathetic to the idea that Moscow should control Kyiv, and the United States had uncovered Putin’s invasion plans and then released them to the entire planet. Most of the world’s biggest economies threatened to hit Russia with sanctions if it went ahead with its attack, and NATO countries made it clear that they would arm Kyiv.