Here’s the point I think we’ve reached: Mr. Putin has run out of possible escalations that wouldn’t just make his situation worse, such as unleashing a nuclear, biological or chemical weapon, or withholding energy exports, or aiming a destructive cyberattack at one or more NATO countries.

If he’s clearheaded at all, any such moves would only rally NATO countries to stronger action and higher tolerance of risk in opposing him, such as discovering enthusiasm for equipping Kyiv with weapons to step up its offensive operations.

Even more crucially, Mr. Putin would risk exhausting the Chinese tolerance on which his regime and personal survival now depend.

Russia has become North Korea: As noxious as the Pyongyang regime may be to Beijing, China has been willing to bear almost any headache to avoid its client being overthrown lest the example infect the minds of 1.4 billion Chinese. Notice I said almost any headache.