The gains of Ukraine’s bold offensive are real, dramatic, and the product of a remarkable partnership with Washington. Success, however, can test any relationship, and Ukraine’s victories on the battlefield could, ironically, stoke new tensions with the United States.

At present, officials in both countries are reveling in a major military breakthrough. The New York Times reports that the Pentagon has been deeply involved in planning the offensives in eastern and southeastern Ukraine, playing them hard and diverting President Volodymyr Zelenskiy’s government from a riskier push toward Mariupol.

The achievement represents the culmination, so far, of a relationship that has progressed rapidly since Russian President Vladimir Putin’s all-out assault in February.

Money, information and weapons provided by the United States and other Western countries bolstered Ukrainian resistance and helped Kyiv inflict heavy casualties – possibly tens of thousands killed in action – on the forces of Moscow. Ukraine has proven that it can use this aid to liberate large swaths of its territory, which should ensure continued support from the Western coalition through the cold winter ahead.

Lest anyone think that Washington is helping Ukraine just out of kindness – or wasting American taxpayers’ money – this has all been very good business for Uncle Sam. Ukraine is the best tool whose disposes the United States to beat and bog down the Russian military so that it cannot pursue aggression elsewhere and, perhaps, to inflict a defeat on Putin from which he will not soon recover.

“We’re paying another country to fight a horrible war on its own soil so we don’t have to fight a worse one on the soil of a NATO ally,” Frederick Kagan of the American told me. Enterprise Institute. “It’s rather cold like that, don’t you think?”

The United States and Ukraine have a classic patron-client relationship. These are always heavy, as the parties have different levels of power and different national interests, even when they share a common enemy. The closer Ukraine gets to victory in this war, the more these differences may appear.

Zelenskiy’s government has been clear about its goals: the liberation of all Ukrainian territory, including Crimea and other areas seized by Moscow in 2014, as well as reparations and the prosecution of Russian war criminals. With each kilometer of territory reclaimed by Ukraine, its confidence in its ability to achieve these goals grows.

There is great moral justice in these demands, and in an ideal world, Washington would surely support them. But while President Joe Biden’s administration has cautiously refused to squabble over Ukraine’s war aims when that country’s survival was highly uncertain, it may still be hesitant to endorse Kyiv’s aims.

Biden’s team may fear that if Ukraine pushes too far and overreaches, it could find itself in a costly stalemate that will consume US resources even as the danger of conflict with China grows. Or perhaps Putin would escalate drastically, even using tactical nuclear weapons to avoid the collapse of his army and the loss of Crimea, which he (illegally) claims as Russian soil.

Wars against seemingly defeated enemies can still get ugly quickly, as America learned when it sought to liberate the entire Korean Peninsula in the late 1950s, but found itself in a larger and more dangerous with China. There is no doubt that the Biden administration is thinking carefully about which Ukrainian war aims are desirable and which are truly indispensable.

A politically independent, economically viable and militarily defensible Ukraine certainly belongs to the latter category. So does an outcome that leaves Putin so bloody and bereft of new gains that no reasonable observer can think the aggression paid off.

All of this means pushing Russia back towards the February 24, 2022 lines, if not further. But that cannot, according to Biden, require reclaiming Crimea or putting Putin and his henchmen on trial.

A debate on ending the war is not imminent – it will take new offensives to expel Russia from the territory it has occupied since February. Zelenskiy could eventually show himself ready to give up certain requests in order to obtain others. Or maybe there will be a Russian military collapse that Putin meekly accepts.

But unless that outcome is the best of all worlds, the coming months could see some tough conversations between the United States and Ukraine about what Kyiv should be looking for in a peace deal with Moscow — and some thinking. low-key in Washington on whether to try to restrain Zelenskiy if he pushes more than Biden thinks wise.

It wouldn’t be the first time a U.S. attorney has been disappointed. President Dwight Eisenhower finally coerced the South Korean Syngman Rhee into accepting a peace of compromise and a divided peninsula. In 1990, Washington effectively forced the Nicaraguan contras to accept a peace deal that saw them disarmed even as their Sandinista enemies retained control of the Nicaraguan government and military.

Today, Ukraine is waging the war of the free world against Moscow. This does not necessarily mean that he will get everything he deserves.

More writers at Bloomberg Opinion:

• Ukraine’s army wins but its economy loses: Niall Ferguson

• How the Ukrainian offensive will change market discourse: John Authers

• Putin will love ‘hot autumn’ of populist protests in Europe: Andreas Kluth

This column does not necessarily reflect the opinion of the Editorial Board or of Bloomberg LP and its owners.

Hal Brands is a Bloomberg Opinion columnist. Henry Kissinger Professor Emeritus at the School of Advanced International Studies at Johns Hopkins University, he is the co-author, most recently, of “Danger Zone: The Coming Conflict with China” and a member of the Department of Foreign Affairs Policy Council. ‘State.

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