Vladimir Putin has been upping his rhetoric, going beyond his perfunctory nuclear threats.

Last month, the Russian leader outlined a much-trailed change to his nuclear doctrine, leading to predictable warnings of a radioactive Armageddon should the U.S. let Ukraine use American-made mid-range missiles against targets in Russia. That was, of course, his purpose.

That most recent change of doctrine should be seen as an attempt by the Kremlin to restore credibility to nuclear threats that are losing their power. It does nothing to remove the enormous hurdles to actually following through with a nuclear attack.