In his press conference in Tokyo on May 23, President Joe Biden said that Russian president Vladimir Putin must “pay a dear price” for his barbaric behavior in Ukraine. That may mean a decisive defeat of Russia, as Poland, Estonia, and other Eastern European members of NATO have urged. It may also mean a restoration of Ukraine’s borders, including Crimea, as President Volodymyr Zelenskyy and other Ukrainian officials are now demanding, as well as the imposition of reparations on Russia for its wanton destruction and crimes against humanity.

Such retributive justice would be condign punishment for Russia’s unprovoked invasion. But would it be worth the cost of more carnage in Ukraine, the possibility of a wider war in which chemical or tactical nuclear weapons might be used, further disruption of the world economy, and renewed European polarization?

In contrast to Russian casualties, only some 3,000 Ukrainian soldiers have died in the war, according to Kyiv. But thousands more civilians have perished, including 10,000 in Mariupol alone. The war has also ravaged Ukraine’s infrastructure and, although precise figures are hard to quantify, the Kyiv School of Economics estimates that the aggregate damage is approaching $100 billion. Even if the war ended tomorrow, the International Monetary Fund reckons that the Ukrainian economy will contract by 35 percent this year.

Amply supplied with arms from the United States and its NATO allies—artillery, Javelin anti-tank missiles, Stinger anti-aircraft systems, drones, and now the M777 howitzer—Ukrainian leaders and military commanders are increasingly confident of victory over the Russian invaders. Buoyed by supportive rhetoric from NATO members—such as calls from U.S. political leaders to weaken Russia and persevere until victory is won and the Estonian prime minister’s declaration that “peace can’t be the ultimate goal”—Ukrainian officials have pleaded for even more lethal weapons.

NATO’s transfer of more advanced weapons, however, could also be self-destructive. Having lost the Cold War in 1991, a paranoid Putin may resort to the use of chemical or tactical nuclear weapons to avert a second humiliating defeat by NATO. A strike against the territory of Poland or one of the Baltic states, as Biden has promised, would invoke NATO’s collective defense clause in the Washington Treaty and expand the war precariously beyond Ukraine.