A picture taken Oct. 8, 2016, shows a general view of the area of Awijah as Syrian pro-government fighters advance in Aleppo's rebel-held neighborhoods. (George Ourfalian/AFP/Getty Images)

It may be no small irony that President Obama’s peripatetic secretary of state will travel this week to Rwanda, where up to a million people were killed in a three-month ethnic genocide in 1994, and has tentative plans to attend an international meeting on Syria, where civilian dead are fast approaching the halfway point of that number.

Bill Clinton, president at the time of the Rwandan massacre, has said that U.S. failure to intervene there is one of his biggest regrets. Just two years later, an estimated 8,000 Bosnian Muslims were slaughtered by Bosnian Serb forces in the town of Srebrenica while “the world’s great nations,” including the United States, “failed to respond adequately,” the United Nations later said.

As Obama constructs the final months of his legacy, both historical events loom large.

“Another Srebrenica, another Rwanda” are “written on that wall in front of us unless something takes place” to stop the slaughter, Staffan de Mistura, the U.N. envoy to Syria, said late last week as Russian and Syrian aircraft and artillery continued their relentless bombardment of rebel-held eastern Aleppo.

There is no consensus within the administration about what the United States can or should do to try to bring a halt to the killing and stop what appears to be the increasingly inevitable fall of Aleppo, Syria’s largest city, to government forces.

The Pentagon has argued for years against direct U.S. military action, seeing that as risking deeper involvement in Syria’s civil war and detracting from the separate fight against the Islamic State in Syria and Iraq. Early last month, defense officials objected to a deal reached with Moscow by Secretary of State John F. Kerry that would couple a cease-fire and delivery of humanitarian aid with U.S.-Russian counterterrorism cooperation against the Islamic State and al-Qaeda-linked forces in Syria.

When the cease-fire fell apart, the Aleppo onslaught began, and Obama ordered up a new assessment and policy alternatives, some senior officials perceived a shift in the Pentagon’s position. At a Sept. 28 meeting of national security deputies, military officials described options against the forces of Syrian President Bashar al-Assad that might provide leverage over Moscow.

Among them were cruise missile strikes against Syrian military activities directly involved in Aleppo operations. The idea, said a nonmilitary official who approved of the concept, was more a shot across the bow to jolt hesitation into a new paradigm, rather than any full-scale U.S. entry into the conflict.

To the State Department and other agencies that had urged a more muscular policy, it seemed that a corner had been turned. Kerry, who has long advocated for U.S. military action, had recently told a meeting of Syrian activists that he had lost that argument long ago, according to a recording of the session obtained by the New York Times. Now the State Department was sure that the Pentagon had switched sides, according to several senior administration officials who described the ongoing, closed-door debate on the condition of anonymity.

But last Thursday, as the discussion moved up the chain to a contentious White House meeting of national security principals, top defense officials made clear that their position had not changed. They advised a possible increase in weapons aid to opposition fighters but said the United States should focus its own military firepower on the anti-Islamic State mission rather than risk a direct confrontation with Russia.

Asked about the perception of a double shift, a senior defense official said the Pentagon’s position had not changed.

“We still believe there are a number of ways to bolster the opposition and not compromise the anti-Islamic State mission,” this official said.

In one drone video, government-held west Aleppo appears verdant and bustling. Another shows rebel-held east Aleppo as a pock-marked wasteland. (Jason Aldag,Ishaan Tharoor/The Washington Post)

But others felt that they had been spun by the defense leadership. Amid increasing internal tension, one senior administration official insisted that both the Syrian opposition and U.S. allies have pressed for a continuation of negotiations and discouraged talk of military intervention. Obama’s position on the subject, this official said, has been “consistent. We do not believe there is a military solution to this conflict. There are any number of challenges that come with applying military force in this context.”

In Obama’s recent speech at the United Nations, the official noted, Obama repeated that “there’s no ultimate military victory to be won” in Syria. Instead, Obama said, “we’re going to have to pursue the hard work of diplomacy that aims to stop the violence, and deliver aid to those in need, and support those who pursue a political settlement.”

No proposals have been presented to Obama for a decision, and some in the administration think the White House is willing to let time run out on Aleppo, in part to preserve options for a new administration.

De Mistura has predicted that if Russian and Syrian air attacks and artillery bombardment do not stop, the city will fall before the end of the year; the U.S. intelligence community assesses that it could be a matter of weeks. While opposition forces expected an Aleppo offensive and were prepared to hold out for months, the airstrikes have systematically targeted infrastructure, such as hospitals, schools and housing, necessary to sustain both rebels and civilians.

An estimated 275,000 civilians, one-third of them children, and 10,000 rebels are surrounded in the eastern side of the city, now under constant aerial attack with what a U.S. intelligence official listed as “barrel bombs, thermobaric bombs, incendiary munitions, cluster bombs and bunker-busters,” with no access to humanitarian assistance or any way out.

While Aleppo is the proximate prize sought by the government and its Russian backers, at least 50,000 opposition fighters — many of whom owe their training, weapons and inspiration in large part to the United States — remain in pockets spread across western Syria.

Many of those forces have been advised and supplied by the CIA, whose director, John Brennan, is said to favor military action or, at the very least, dispatching more and better weapons to the opposition, particularly if Aleppo is lost.

That decision, which would allow the rebels to continue to fight a guerrilla war, or to defend those pockets of the country still in opposition hands, might not be the administration’s to make. Allied governments in the region, including Qatar, Turkey and, to a lesser extent, Saudi Arabia, have long advocated for increased support for the rebels and could decide on their own to send more sophisticated armaments — some of which, including shoulder-launched antiaircraft weapons, the United States has refused to make available on the grounds that they could end up in the wrong hands.

As they assess Russian President Vladi­mir Putin’s goals in Syria, intelligence officials think he is less interested in an outright military victory than in being able to set the terms for a settlement that ensures Assad’s survival. But at least in the short term, they believe, the big winner may be the Front for the Conquest of Syria, the al-Qaeda affiliate formerly known as Jabhat al-Nusra.

The jihadist group, which U.S. officials have said is planning “external operations” against the United States, has grown in strength and respect as a formidable, well-equipped fighting force against Assad.

While senior White House aides are said to be opposed to U.S. military action, one other official who is said to have argued in favor of a military response is Samantha Power, the U.S. ambassador to the United Nations, whose award-winning book on the failure of policymakers to stop genocide in Rwanda and elsewhere first brought her to Obama’s attention.

Echoing the arguments for accountability in the book, “A Problem From Hell,” Kerry last week publicly called for Russia and Syria to be investigated for war crimes for the targeted killing of civilians and wanton destruction in Aleppo and beyond.

On Friday, Moscow described Kerry’s call as “propaganda” and repeated its assertion that the United States, by failing to separate rebel forces from the targetable terrorists it insists control Aleppo, is to blame for the failure of the cease-fire.

According to international-law experts, however, the likelihood of a war crimes prosecution of either country is virtually nonexistent. Neither Russia nor Syria belongs to the treaty-based International Criminal Court, and a referral to its jurisdiction would require a resolution by the U.N. Security Council, a body in which Russia holds a veto. At the same time, both the ICC and the International Court of Justice, the United Nations’ judicial branch, are designed to prosecute individuals rather than states.

“The law of war crimes is individual and personal,” said Kenneth Anderson, a law professor at American University.

“Talk of war crimes trials by itself is not serious,” Anderson said. “It’s an evasion of policy by a state that does not want to have to respond to the concerted actions of another state, another two states.”