The man beside him was carrying a briefcase.

That briefcase appeared to be Russia's version of the "football" that is carried by a military aide to U.S. presidents and contains the codes for launching strategic nuclear weapons.

French King Louis XIV had stamped upon his cannon the inscription, "Ultima Ratio Regum" — The Last Argument of Kings.

In our era, nuclear weapons are the ultima ratio of nation-states. And what Putin was saying with his briefcase-carrying aide beside him was that, rather than accept defeat and humiliation in the Ukraine war, he may resort to the use of tactical atomic weapons.

And Putin is not the only one reminding us of the utility of having nuclear weapons and the folly of giving them up.

In 1991, when the Soviet Union dissolved into 15 nations, a newly independent Ukraine controlled its own large arsenal of nuclear weapons.

At the behest of the United States and in return for U.S. security guarantees, Kyiv gave them up and sent them all back to Russia.

Ukraine is living today with the consequences of that decision.