The Russian invasion of Ukraine is a watershed moment not of a European, but also of a global aspect. Far greater in importance than the 9/11 attacks. Books will be written, and history will use it as a marker for the onset of a new (who knows if it will be cold) war. Coincidently, in one of my IR classes yesterday we were talking about the Berlin blockade and the onset of the previous, thankfully Cold war. So my students tried to use some system theories to explain the conflict and to draw parallels with the current situation. But, they were running into a problem. Taken over time, realism seemed to explain well the Cold war conflict, but was falling short to provide a satisfactory explanation for the behavior of the US since its end, while liberalism with its emphasis on cooperation, interdependence, etc. was failing to account for Russia's and Ukraine's behavior in the immediate runup to the Russian aggression. Then, it dawned on me, that the two main great powers in this...