Russian President Vladimir Putin’s endgame in Ukraine remains unclear.

But his war there does seem to be sending one clear message: if you have nukes, nobody messes with you. The security risks this poses cannot be overestimated.

Just days after launching his invasion of Ukraine, Putin announced that he had placed Russia’s nuclear forces on “high alert” — a clear warning to the West not to intervene militarily on Ukraine’s behalf. And it seems to have worked. Despite Russia’s relentless bombardment, including of civilian areas, the United States has flatly refused Ukrainian President Volodymyr Zelensky’s repeated requests for a NATO-enforced no-fly zone.