NOW THAT the “Geneva 2” conference on Syria has collapsed, Secretary of State John F. Kerry is trying to distance himself from the wreckage of an initiative that he made the focus of the Obama administration’s Syria policy for nine critical months. Last Sunday, after the talks between the regime of Bashar al-Assad and a Western-backed opposition coalition ended in impasse without a renewal date, Mr. Kerry issued a statement blaming “the Assad regime’s obstruction” for the failure. In a news conference the next day he faulted Russia for “enabling Assad to double down” on the battlefield “rather than come to the negotiating table in good faith.”

Mr. Kerry’s analysis is correct, so far as it goes. The Assad regime made no pretense of taking seriously the nominal purpose of the Geneva talks, which was to agree on a cease-fire, the opening of corridors for humanitarian aid and a transitional government acceptable to both the government and the opposition. Nor did Russia pressure its ally to go along with that agenda. Instead, both tried to turn the talks into a forum for discussing how to combat “terrorists” in Syria — a label that Damascus and Moscow apply not just to al-Qaeda but to all armed groups that oppose the regime.

That still leaves the question of why Mr. Kerry spent months insisting that Mr. Assad and his Russian backers would go along with a negotiated settlement — and therefore that pursuing Geneva 2, as opposed to more robust measures to stop the mounting bloodshed, was the best U.S. policy. Prior to launching the Geneva 2 effort last May, Mr. Kerry had been a proponent of “changing the calculations” of the Assad regime by providing more military support to the opposition.

Following a visit to Moscow and a meeting with Vladi­mir Putin, however, Mr. Kerry abruptly changed his tune. At a May 7 news conference he heaped praise on Mr. Putin for a discussion that “contributed significantly to our ability to map a road ahead.” He declared that Russia and the United States “are going to cooperate in trying to implement” a plan under which “the government of Syria and the opposition have to put together, by mutual consent, the parties that will then become the transitional government.”

“Our understanding” of the plan, Mr. Kerry said of himself and Mr. Putin, “is very similar.”

The first question on that first of many occasions when Mr. Kerry touted the Geneva 2 formula was telling. Asked a reporter: “What makes you think that President Assad would be willing to take part in a negotiated political solution if, as the United States has repeatedly said, he must leave power?” The obvious answer: Mr. Assad wouldn’t. But for nine months Mr. Kerry stubbornly insisted that just that scenario would unfold. As late as Jan. 16, when even U.N. mediator Lakhdar Brahimi was trying to focus Geneva 2 on the more modest goal of providing humanitarian aid to one neighborhood in one city, Mr. Kerry reiterated that the conference’s “sole purpose” would be to create a transitional government.

Mr. Kerry’s calculus was that even if Mr. Assad were not willing to step aside for such a government, he would be pressured into it by Mr. Putin. But there was never any good reason to believe the Russian ruler — who employed scorched-earth tactics similar to those of Mr. Assad to subdue an uprising in the Russian republic of Chechnya — would support the U.S. goal. On the contrary, Mr. Putin stepped up weapons deliveries to the regime, blocked efforts at the United Nations to open humanitarian corridors to civilian areas under siege by regime forces and echoed the propaganda that Syria’s main problem was “terrorism.” Not for the first time, Mr. Kerry and the Obama administration badly misjudged the Russian leader.

Throughout the last nine months, Mr. Kerry claimed that his transparently futile initiative was worthy because, as he put it in Moscow, “the alternative is . . . even more violence . . . the alternative is that Syria heads closer to an abyss, if not over the abyss, and into chaos.” Yet that is exactly what happened in the following nine months. Chemical weapons and barrel bombs were dropped on civilians, al-Qaeda strengthened its hold on parts of eastern Syria, and many thousands died — all while the United States eschewed steps to stop the carnage on the grounds that the Geneva 2 talks offered, as Mr. Kerry put it, “the best opportunity for the opposition to achieve the goals of the Syrian people.”

In that assessment, Mr. Kerry was profoundly wrong. Now he says that “the international community must use this recess in the Geneva talks to determine how best . . . to find a political solution.” But more appeals to the world will not end Syria’s nightmare or the growing threat it poses to vital U.S. interests. That can be addressed only by a new U.S. policy, one that aims at directly weakening the Assad regime’s ability to wage war and that strengthens the moderate forces opposing it and al-Qaeda. It won’t happen in Geneva.