From the outset of the conflict, nuclear weapons have loomed large. Putin has repeatedly drawn attention to Russia's nuclear capabilities as a means of deterring the United States or NATO from intervening in Ukraine. Now that the conflict is going more poorly than Putin anticipated and he is facing strong economic pressure from the West, he has alerted Russian nuclear forces in order to bid up the nuclear risk even further.
While Putin's primary audience for his nuclear signaling is NATO, we shouldn't entirely dismiss the possibility he would consider using low-yield nuclear weapons against Ukraine if he thought his campaign was on the brink of failure or becoming too costly. Russia's nuclear strategy envisions possible first use in dire scenarios and Putin's rhetoric and behavior suggests he may view the future of Ukraine as an existential issue.