What can be done now to change Putin’s calculations, or to respond to an invasion?

The U.S. and NATO countries should begin active cyber-warfare countermeasures to help defend Ukraine from ongoing Russian attacks on its computer networks and infrastructure. In this realm, the  U.S. may have the most advanced capabilities, and should begin using them now. Above all, U.S. decision makers should avoid undue hesitance by  demanding absolute proof of attribution of the attacks. In a wartime setting, officials and nations may need to act in the absence of perfect information.

If Russia is not behind the attacks, who do U.S. analysts and policymakers think is? Nigeria? Lesotho? Fiji? It is immaterial whether the operators are Russian officials or others acting under their control.

Finally, in order to influence Putin’s calculations at this late stage in the game, NATO members should leave open the possibility of coming to Ukraine’s defense through the use of military force and active cyber-warfare measures, in exercise of the right of collective self-defense under Article 51 of the U.N. Charter, if Russia invades Ukraine and a major war develops.