European defense policy is in disarray, as the continent edges toward likely escalation with a nuclear-armed Russia. Calls for Ukraine to use North Atlantic Treaty-supplied weapons to strike inside Russia juxtapose with proposals from President Macron and Germany’s Olaf Scholz that climate policies are the solution to Europe’s problems. Meanwhile, European trade with Russia continues via Kazakhstan. Urgently needed is clarity. 

The imperative of a Ukrainian victory is clear — whether or not Kyiv’s success might deter Communist China. An emboldened Russia threatens Europe beyond its eastern flank. This has been true since the war began. So it has been curious to observe much of Europe hesitate to provide Kyiv with the tactical support needed to defeat Moscow. France has contributed 2.7 billion euros in military aid. 

This compares to Poland’s 8.4 billion and Denmark’s 4.7 billion euros, though Poland’s gross domestic product is one-fourth of France’s and Denmark’s about 15 percent. Yet the French president is now calling for Ukraine to be able to strike military targets within Russia and French troops to forward deploy to Ukraine. NATO’s secretary general and leaders from Sweden, Denmark, and Lithuania make similar calls.

Britain’s foreign secretary, David Cameron, also affirms Ukraine’s “right” to use British-supplied weapons for attacks in Russia, an idea endorsed by Secretary Blinken. France is set to send military instructors to Kyiv. Poland suggests it could deploy troops should Moscow advance. This is risky. Europe for two years watched as Moscow made gains in Ukraine and expanded its defense industrial base. Russian artillery shell production is today triple Ukraine’s allies.

If, then, Russia is such an existential threat to European security — which, arguably, it is — why has Europe dithered until the ostensible eleventh hour to mobilize, and to do so in such a potentially escalatory way? This too, in the continued absence of a defined strategy for victory and a desired end-state. Renewed commitments to support Ukraine “for as long as it takes to win” no longer suffice. At this point, what does that even mean?

And what might such support look like if, say, Moscow were to strike NATO assets in or beyond Ukrainian borders in response to attacks from Kyiv? President Putin has said Europe should “remember that, as a rule, they are states with a small territory but dense population,” raising the risk of nuclear confrontation. No doubt, such a risk has loomed over every conflict between nuclear powers since nukes entered the strategic equation.

Aware of the transatlantic community’s fear of a nuclear contest, too, Moscow brandishes the threat at opportune moments to deter escalation. Mr. Putin could be bluffing. Or not. Among the lessons the war should have taught Western leaders is humility in their assumptions, many of which have so far proven wrong. It would then be hasty to assume Moscow won’t resort to nuclear war because it hasn’t yet or because it wouldn’t be “rational.”

Moscow’s cost-benefit calculations diverge from those of many Western actors. Missing from European defense debates, then, is a certain gravity. Yet this is exactly what is needed amid calls for Ukrainian strikes in Russia with Western arms. In a Russian counterattack, for instance, Europe would be unable to defend itself. It lacks air defenses, heavy equipment, ammunition, and the ability to sustain ground forces for more than a few weeks.

The assumption, presumably, is that America would intervene. But under what conditions? Would a Russian offensive against NATO troops voluntarily forward deployed in Ukraine trigger Article 5? Given our stretched military capabilities, would we be able to adequately support our allies — or willing, considering Europe’s persistent economic dalliances with Moscow and our strategic priorities in other conflict theaters?

The point is not to hinder Ukraine from bolstering its defenses, including through retaliatory measures. Retaliation is a central tenet of warfare. Yet, if Europe ultimately embraces such a policy that so significantly binds it to Ukraine’s conflict with Russia after years of strategic dawdling, it must do so decisively. It must outline a clear end to the war and the means to achieve it. Defense priorities must outweigh climate considerations.

Trade with Russia through Central Asia must stop. Europe might also consider redirecting some of the 40 percent of shells it continues to produce and export overseas to Ukraine. Needed, too, are contingencies for how NATO would respond to a Russian attack on allied assets. This is not an academic exercise. This is war — and should Europe allow NATO-supplied weapons to strike inside Russia, it has just upped the stakes.