As the Russo-Ukrainian War grinds on, both Russia and Ukraine have adjusted their strategic objectives. Russia abandoned its initial goal of seizing Kyiv and installing a pro-Russian government after facing fierce Ukrainian resistance, and is now focusing on conquering Eastern Ukraine and annexing significant portions of Ukraine’s southern territory. Ukraine’s minimum objectives include reestablishing its prewar borders, with political leaders occasionally suggesting that Ukraine should expand its ambitions to reclaiming territory lost to Russia in Crimea and the Donbas region since 2014.
U.S. strategic objectives in Ukraine are also a moving target. Secretary of Defense Lloyd Austin stated that the United States not only wants Ukraine to remain a sovereign and democratic country, but also “to see Russia weakened to the degree that it can’t do the kinds of things that it has done in invading Ukraine.” Speaker of the House Nancy Pelosi promised that the United States would support Ukraine “until the fight is done.” President Joe Biden reiterated this point, stating that the United States would support Ukraine for “as long as it takes so Russia cannot, in fact, defeat Ukraine and move beyond Ukraine.”
Analysts and commentators debate how ambitious U.S. support for Ukraine should be. Some scholars have emphasized differences in U.S. and Ukrainian interests and encouraged more limited objectives. Calls for continued and expanded military support have come to dominate the defense policy discourse.
A core point of disagreement between these two camps is the perceived likelihood of nuclear escalation. Whereas those arguing for limited objectives tend to worry about the potential for escalation across the nuclear threshold, analysts in favor of increased support for Ukraine view the costs of concessions as more dangerous than confrontation and tend to view the likelihood of escalation as minimal.
The likelihood of nuclear use in Ukraine may be low, but it is not zero. Analysts who quickly dismiss the potential for nuclear escalation—and even most of those who express worries about nuclear conflict—largely oversimplify the many pathways that can lead to nuclear use, whether purposeful or inadvertent. Providing a clearer delineation of those pathways will help policymakers better understand which policy options can more safely advance U.S. objectives, and which policies should inspire greater caution and restraint.