Opinion | Ukraine in NATO? My heart says yes. But my head says no.

There is also little doubt that NATO expansion has been a powerful force for peace and stability in Europe. The very reason Russian dictator Vladimir Putin is invading Ukraine — rather than Poland or the Baltic states, which were also once part of the Russian Empire — is that those other countries are in NATO and Ukraine is not. For all of Putin’s bravado, he does not want to risk a conflict that would trigger NATO’s Article 5 collective security guarantee, including the ultimate deterrent provided by the United States’ nuclear forces. It’s bunk to say, as Kremlin apologists do, that NATO expansion to Eastern Europe has caused Russian aggression. The illiberal nature of Putin’s regime accounts for its aggression — and the Kremlin would be a far greater threat if Putin knew he could attack more of Russia’s neighbors with impunity.

Yet there is deep and understandable reluctance among Western European states and the United States to admit Ukraine to NATO, because it is at war with Russia and will be for the foreseeable future. This isn’t a stable stalemate like the division of East and West Germany or North and South Korea. This is a dynamic, ongoing conflict that, if NATO were to take in Ukraine, could draw other members into a shooting war with a nuclear-armed Russia.

It’s true, as Scheunemann and Farkas argue, that Article 5 — which holds “that an attack against one Ally is considered as an attack against all Allies” — “does not mandate a specific response by member states.” NATO members could say they are complying with Article 5 by doing what they are already doing: supplying Ukraine with weapons, training and intelligence and imposing sanctions on Russia. But there has always been an implicit assumption that an armed attack on a NATO member would result in military action by other NATO members. If that’s not the case, it would risk watering down Article 5 and reducing the overall effectiveness of the NATO alliance. Do we really want to send a message to Putin that he could invade, say, Lithuania and the West won’t fight to defend that embattled democracy?

NATO could try to skirt that difficulty by announcing that Ukraine will not be admitted now but in the future, once its war with Russia is over. But that would create a perverse incentive for Russia to keep fighting so as to prevent Ukraine’s entry into the transatlantic alliance. NATO should not make the same mistake it made at its Bucharest summit in 2008 when it declared that it “welcomed” the “aspirations” of Ukraine and Georgia to “become members of NATO” but did not agree on a Membership Action Plan to turn aspirations into reality. That only increased Putin’s incentive to attack those countries before they were granted admission to NATO — as he did with Georgia in 2008 and Ukraine in 2014.

The good news is that, even without admitting Ukraine, it is possible for NATO members to bolster long-term security ties with Kyiv and make clear to Russia that it will never be able to destroy Ukraine’s freedom. As Eric Ciaramella of the Carnegie Endowment for International Peace argued in a recent policy paper, Washington’s relationships with Israel and Taiwan point the way. Neither is a treaty ally, but in both cases, the United States is bound by law and diplomatic agreements to arm them so that they can resist aggression.

Since the 1973 Yom Kippur War, which Israel nearly lost, successive U.S. administrations have pledged to help the Jewish state maintain a “qualitative military edge” over its Arab neighbors. This concept was eventually codified by Congress into law. The United States and Israel have also negotiated a series of “memorandums of understanding” that commit Washington to provide fixed levels of aid. (The most recent memorandum, signed in 2016, pledges the United States to provide $38 billion in military aid between 2019 and 2028.) These U.S. commitments have allowed the Israel Defense Forces to remain the most powerful military force in the Middle East.

The United States ended its formal military alliance with Taiwan in 1979 when it established diplomatic relations with Beijing. But at the same time Congress passed the Taiwan Relations Act, which states that Washington will sell weapons to Taiwan so that it can “maintain a sufficient self-defense capability” and that the United States will “resist any resort to force or other forms of coercion that would jeopardize the security … of the people of Taiwan.” The United States has not provided Taiwan with nearly as much military aid as Israel, but U.S. support has allowed Taiwan to remain de facto independent of the Communist regime on the mainland.

These are the models that the United States should follow with Ukraine. The Biden administration should pledge that the United States will provide sufficient weapons, training and intelligence support to allow Ukraine to maintain its sovereignty (preferably within the 1991 international borders), and Congress should write that pledge into law. If a Republican-controlled House agrees, that would provide a powerful signal of bipartisan support for Ukraine. Other NATO members should make similar pledges.

It is also imperative for the West to provide a continuing stream of monetary aid to ensure Ukraine’s economic viability despite the war, which has devastated its industrial and agricultural base. The European Union should take the lead in offering Ukraine a road map to membership — which would force Ukraine to take tough action against corruption in return for eventual access to E.U. subsidies. Western countries should also pledge to turn over to Ukraine roughly $300 billion in Russian funds frozen in Europe and the United States to finance the reconstruction of war damage.

Even without offering the guarantees of Article 5, NATO states can greatly strengthen Ukraine’s capacity to resist Russian aggression over the long term and make clear to Putin that this is a war he cannot win.