Russia’s invasion of Ukraine, now in its seventh week, shows no sign of abating. Vladimir Putin’s army has abandoned its assault on Kyiv, Ukraine’s capital, but is launching a new offensive in the country’s east. Ukraine’s allies, led by the United States and Britain, have stepped up their supplies of tanks and anti-aircraft weapons.

But every war must end some day, whether in a victory for one side or a split-the-difference cease-fire. In Washington and other Western capitals, debate has begun over what terms Ukraine and its allies should seek for ending this one — or what goals they should hold out for.

At first glance, the question might appear simple: Ukraine and its allies want Putin to end the invasion and withdraw his troops. But the details get complicated quickly.

Some U.S. and European hawks see the unexpected success of Ukraine’s armed forces as a golden opportunity to cut Putin down to size and teach a lesson to other autocrats, beginning with China’s Xi Jinping.

“The Western objective must be to leave Russia profoundly weakened and militarily crippled ... internally divided until the point that an aging autocrat falls from power,” Eliot A. Cohen of Johns Hopkins University, a former official in the George W. Bush administration, wrote recently.

But doves worry about threatening Putin’s survival in power to the point that he might consider using nuclear weapons. And some European leaders, led by French President Emmanuel Macron, have searched for a quick end to the war, if only to reduce the damage to their own economies.

In the middle, President Joe Biden and his aides have settled on what sounds like an elegant solution: endorse whatever outcome is acceptable to Ukraine.

“Our job is to support the Ukrainians,” Biden’s national security adviser, Jake Sullivan, said recently. “They will set the military objectives. They will set the objectives at the bargaining table.… We are not going to define the outcome of this for the Ukrainians. That is up for them to define and us to support them.”

The logic is straightforward: The Ukrainians are doing the fighting and suffering horrendous civilian casualties, so they’ve earned the right to decide what kind of settlement they’re willing to accept.

“As long as the Ukrainians are saying they want to keep fighting, we can’t tell them no,” argued Steven Pifer, a former U.S. ambassador to Kyiv.

Ukraine’s president, Volodymyr Zelenskyy, offered Putin terms for a cease-fire last month and included several concessions: He asked for a Russian withdrawal to the lines each army occupied before the Feb. 24 invasion, which would leave several chunks of Ukrainian territory in Russian hands. He said Ukraine would accept neutral status and give up its effort to become a member of NATO. In return, he said, Ukraine would need ironclad security guarantees to prevent another invasion.

Putin’s aides dismissed the offer as inadequate.

That was before the discovery of widespread atrocities against civilians by Russian troops north of Kyiv, which may have hardened Ukraine’s resolve to keep fighting. Zelenskyy has said he would submit the terms of any cease-fire to a referendum.

In any case, deferring to the Ukrainians on terms for ending the war is more complicated than it sounds because the likely terms will require active participation by the United States and its allies.

Take Zelenskyy’s demand for security guarantees. He wants a reliable, binding pledge that if Russia invades again, the United States and its allies will step in with the kind of sanctions and military aid they are supplying now, or more.

“Whether Russia agrees to a settlement or not, Ukraine is going to need security guarantees,” Ivo H. Daalder, a former U.S. ambassador to the North Atlantic Treaty Organization, told me.

“There’s already an organization that does that, and it’s called NATO. … How is NATO going to say no to membership for Ukraine after all of this has happened?”

Another thorny issue will involve U.S. economic sanctions. In any talks over ending the war, Russia is certain to demand that sanctions be lifted. U.S. officials have said that sanctions relief will be up for discussion, but only after Russian troops are out of Ukraine.

“But that was before Bucha,” Daalder said. “The atrocities have made it much more difficult to contemplate lifting any sanctions.”

If a cease-fire takes hold, the United States will also be expected to play a leading role in helping Ukraine rebuild its armed forces, its economy and its shattered cities.

U.S. and allied support after the war will be just as important as it is now. Putin has invaded Ukraine three times since 2014; if his current offensive falls short, he can be expected to plan a fourth. One goal for U.S. policy should be to deter him from trying again.

The most damaging outcome for Putin would be a Ukraine that can regain its independence, defend its borders and show Russians that democracy can prosper in their part of the world. For anyone seeking to settle scores, that would be the best revenge.

Doyle McManus is a columnist for the Los Angeles Times.