To do so, the U.S. should pledge commensurate nuclear retaliation to any Russian nuclear strike against NATO. Washington should also make clear that a nuclear attack on Ukraine will result in Biden’s request to Congress, and request for allied support, for an authorization of military force to repel Russian forces from Ukraine. Biden should make the same pledge in relation to scaled Russian chemical or biological weapons attacks on Ukrainian cities.

Biden’s immediate clarity is crucial in light of his worrisome nuclear weapons policy record. This record is something that Russian intelligence officers, and Putin personally, will have paid very close attention to.

Consider the now senior Pentagon official and former national security adviser to then-Vice President Biden, Colin Kahl. Kahl appears to have recently told Max Fisher that during an Obama administration nuclear war game, he “persuaded” U.S. military commanders to forgo nuclear retaliation following a limited Russian nuclear strike. Instead, Kahl had the U.S. “isolate Moscow diplomatically.”

This is an insane message to send so publicly to Moscow, especially now. More than any other nation, Russia’s nuclear strategic doctrine rests on the exploitation of apparent hesitation and Moscow’s associated dominance of the escalation curve. To deter Putin effectively, the Russian leader must thus know that the costs of any nuclear action will far outweigh any prospective benefits. Put another way, Russia must take the exact opposite understanding of that which Kahl (remember, he’s now the Pentagon’s top policy official) appears proud to publicize.