How do you monitor a skeleton of a city bereft of its citizens, who have been bused out after seeing their homes bombed to pieces by barrel bombs from the Syrian regime and bunker busters from their Russian supporters?
And what will be left to watch when -- and if -- the monitors ever arrive?
In the best-case scenario, the United Nations observers in Aleppo may find out.
In a rather realistic one, the world will never know.
At long last, the United Nations Security Council has been able to agree on something.
That something is the monitoring of the evacuation of the children and parents, men and women left alive in Aleppo, after the siege of their city -- starved on the ground, bombed from the sky and sealed in without any refuge or non-lethal path to escape -- grew inhuman enough to prick the world's conscience and puncture its longstanding indifference to Syria's carnage.
Too grotesque to ignore
The YouTube war finally became too grotesque to ignore.
An overnight crisis, years in the making, finally grew impossible to overlook.
The UN resolution called for "adequate, neutral monitoring and direct observation on evacuations" and demanded that all sides provide the monitors "with safe, immediate and unimpeded access."
But in reality, the French-backed resolution that finally won Russian and Chinese support says that those observers can only enter after they consult with "interested parties," a verbal umbrella which is likely to include a bevy of forces backing Syrian President Bashar al-Assad, from Iran to Russia.
By the time these neutral observers do make it in, eastern Aleppo likely will be cleared of the parents who called the city home and found themselves forced to flee when they could no longer send their children to play on their own streets or attend the city's schools.
Starved into submission, stripped of medical supplies in hospitals left without power, anesthesia and, increasingly, doctors, who could survive the bombardment of the Syrian regime and its Russian air supporters? They could bear no more. Who could?
Even the remains of the fractured international community couldn't take its impotence being called so painfully and embarrassingly to account by the images coming out of Aleppo.
How many pictures of grieving parents reaching toward the sky and dust-covered babies bombed to the ground could the world stomach?
Syria is the war that has run out of adjectives
Words long ago failed to describe its depravity -- or to rouse the international community to do anything other than look away and wait for it to end.
UN officials themselves have called out their institution's ineffectiveness in the face of Aleppo's brutality.
"Since September, the Security Council has failed to adopt three resolutions that could have enabled a humanitarian truce, evacuation of civilians and the entry of lifesaving aid," said Ban Ki-moon, who just stepped down from the UN helm.
A UN release noted that on "8 October, Russia vetoed a resolution that would have called for an end to military flights over Aleppo; and on 5 December, a measure calling for a seven-day ceasefire in the beleaguered city failed to pass after negative votes by both China and Russia. In all, Russia has vetoed six texts on the Syrian conflict, while China has vetoed five of those six."
As he took leave of UN leadership last week, Ban said that "Aleppo is now a synonym for hell."
He also noted: "We have collectively failed the people of Syria."
He is right on both counts.
Can the UN's next leader do any better?
The question is whether his successor, Antonio Guterres, can do any better, given that the Syrian regime, along with Russia and Iran, have now shifted facts on the ground dramatically in their favor.
And now, with Aleppo's fall, they have successfully implemented their starve-versus-surrender strategy in Syria's major cities.
Years ago, as the head of the UN's Refugee Agency, Guterres said he had run out of descriptors for Syria's civil war.
Today he is the head of the United Nations, facing the task of implementing this latest resolution.
The UN Security Council's unanimity breakthrough is months, if not years, too late for this resolution to make a difference for the 4 million made refugees, the more than a quarter-million dead and the millions displaced inside the country, who have absolutely no place safe to turn and no place outside the nation's borders eager to offer them safety.
Syrian activists and those inside the Obama administration who favored greater intervention in the conflict both tell me they fear the fate of those fleeing Aleppo to the town of Idlib, which is likely to be next in Assad's crosshairs.
And they wonder how it took this much death to finally see Syria seize the global stage?
"I never thought we would be forced to leave our homes," Khokoud Helmi, a founder of the Syrian underground newspaper Enab Baladi, told me.
"Shall we have lost all these lives to finally have people standing with us? It is too late, dear, but late is better than never."
Gayle Tzemach Lemmon is a senior fellow at the Council on Foreign Relations and author of the New York Times best-seller, Ashley's War: The Untold Story of a Team of Women Soldiers on the Special Ops Battlefield. The opinions expressed in this commentary are hers.