Over the last year Russia’s invasion of Ukraine has produced a flood tide of commentary, with largely unconstructive volleys back and forth. Roughly speaking there are two main camps. Realists and progressives blame Russia’s invasion principally, sometimes solely, on NATO expansion—a needless, provocative policy that, as they see it, posed an “existential threat” to Russia. Neoconservatives and many liberal internationalists, despite their political differences on other fronts, deny that NATO expansion had this effect, and even claim that it was wholly irrelevant to Putin’s decision to attack Ukraine. Instead, they see Putin’s ingrained imperial instincts and fear of a democratic Ukraine as the root cause of the war.