Political science and history tell us a lot about how authoritarian regimes start, persist and end. In highly personalized regimes like Mr. Putin’s Russia, rulers often fight to the bitter end, and the regime that follows typically isn’t democratic.

Further, a post-Putin Russian regime would rule the same country—the world’s most vast by far, with relatively indefensible and porous borders. Sitting as Russia does at the crossroads of Eurasia, its borders have for centuries been the object of rivalry and conflict with neighbors to the west, east and south. By one estimate, since 1800 Russia has experienced an invasion from its west about once every 33 years on average.

The result has been a nearly permanent sense of weakness and insecurity within Russia. That has fueled a domestic political environment in which those who pursue confrontation and opposition in foreign policy—whether czars, Politburo chairmen or presidents—tend to realize greater political success than those who favor cooperation and integration.