A good summary of the realist perspective on how the 2022 war in Ukraine started.
Missing are the details of Russia’s original invasion of Ukraine in 2014. Actually, invasion is the wrong word. Russia’s early engagement in the Donbas was somewhat like the U.S. early engagement in the Vietnam war. That is, Russia at first provided materiel and advisory support to an indigenous Donbas resistance against Kiev. This later escalated to providing boots on the ground to support the Donbas local militias. One could say that Russia’s invasion of Ukraine back in 2014 was by invitation, but this nuance is ignored by many commentators.