They could match the move and put American forces on Defcon 3 — known to moviegoers as that moment when the Air Force rolls out bombers, and nuclear silos and submarines are put on high alert. Or the president could largely ignore it, sending out aides to portray Mr. Putin as once again manufacturing a menace, threatening Armageddon for a war he started without provocation.

For now, at least, Mr. Biden chose to de-escalate. The American ambassador to the United Nations reminded the Security Council on Sunday afternoon that Russia was “under no threat” and chided Mr. Putin for “another escalatory and unnecessary step that threatens us all.” The White House made it clear that America’s own alert status had not changed…

Others wonder if Mr. Putin wants to create that impression, to add to Washington’s unease. Similar concerns drove the decision not to have Mr. Biden, in Delaware for the weekend, respond to Mr. Putin’s threats. It was the second time in a week that Mr. Putin has reminded the world, and Washington, that he has a massive arsenal and might be tempted to use it. But what made the latest nuclear outburst notable was that it was staged for television, as Mr. Putin told his generals that he was acting because of the West’s “aggressive comments” about Ukraine. Russia’s most senior military officer, Valery Gerasimov, sat stone-faced as Mr. Putin issued his directive, leaving some wondering what he was thinking, and how he might respond.