But such talks were never presented to Russia as a formal diplomatic offer.

Charles A. Kupchan, who is the European director of the National Security Council at the Obama White House, said Putin’s tacit response to such talks showed that a more explicit proposal to distance Ukraine from NATO would be futile.

“Is the body language coming out of Washington, Kyiv and every European capital enough to provide a trading space if he wants it? Yes. But he doesn’t seem to pick it up,” said Kupchan.

“I think going back to the early 1990s, America’s foreign policy establishment too easily rejected Russia’s objections to NATO expansion,” he added. “That being said, as I step back from the events of the last few months, the prospect of Ukraine joining NATO seems more like a smokescreen to me than the heart of the matter” to Putin.

Andrew S. Weiss, head of the Russia and Eurasia program at the Carnegie Endowment for International Peace, said Russia had made impossible demands from the start, but the illusion of diplomacy fueled political debate in the West that served Mr. Weiss. Weiss. Putin’s goal. Moscow, he said, is focusing “quite shrewdly on ancient complaints about Ukraine’s theoretical eligibility for NATO membership, knowing full well that these issues provoke many in the West.”

The United States is engaged in “stale and predictable academic debate with ourselves about whether past administration policies were provocative towards the Kremlin,” Weiss said. Those discussions, he added, were played in the hands of “isolationists like former President Trump who argued that the US alliance was an unnecessary burden and America would be better off defending the border with Mexico.”

“In Europe, where anti-Americanism and Ukrainian fatigue are just beneath the surface, the Potemkin Kremlin’s diplomatic moves are also paying off,” Weiss said.

Kori Schake, director of foreign and defense policy studies at the American Enterprise Institute, said it was difficult to know if Putin had ever taken diplomacy seriously. But he said he might expect the extreme pressure of an invasion to break the West and win some concessions for it. “After belittling Western unity, he may feel trapped and can’t back down without showing anything,” he said.