Syrian residents fleeing the violence gather at a checkpoint, controlled by pro-government forces, in the Maysaloun neighborhood of the northern embattled Syrian city of Aleppo on Dec. 8, 2016. (Youssef Karwashan/AFP/Getty Images)

Troops loyal to Syrian President Bashar al-Assad have retaken much of the rebel-held neighborhoods of Aleppo in the past week, signaling the imminent end of a withering siege that has lasted years and hollowed out what was once the country's biggest urban center. On Wednesday night, a fragile cease-fire came into effect, allowing civilians trapped inside rebel areas to flee and giving relief workers and humanitarian organizations access to help those most vulnerable to the conflict.

Hundreds have died in the past three weeks, as the regime, backed by Russian airstrikes and a hodgepodge of allied militias, closed in on the last strongholds of rebel factions.

“Inside what remains of the rebel enclave, there is a growing humanitarian crisis,” my colleague Louisa Loveluck reported. “Amid blistering bombardment, thousands of residents displaced by the offensive now shelter inside abandoned apartment blocks.” Many were in need of medical evacuation.

On Thursday, the BBC published a letter submitted anonymously by a doctor working for the International Committee of the Red Cross. Along with his team and members of the Syrian Arab Red Crescent, they journeyed to what was formerly an old people's home in the heart of Aleppo's Old City, once one of the bigger tourist draws in the Middle East but now a warren of rubble and ruin.

“I have seen many things in Syria during the past five years,” the doctor wrote. “But nothing like this.” Here's an excerpt of what he encountered (you can read the grim story in full here):

In the midst of the landscape, two crumbling buildings. One building for the men, one for the women.

We entered the yard. A group of patients sat huddled round an open fire. They had few clothes and were shivering. Many looked bemused. They were very near to each other, pushing their shoulders together, looking around, trying to reassure one another.

To one side, there were bodies, maybe around 10 of them.

I knew the man who ran the centre and we found him. We learnt that he'd lost his entire family three days earlier: among them, his wife, son and grandson. He'd brought his family here because he thought no one would attack the centre.

Some of the bodies in the yard were members of his family.

As darkness closed in and temperatures dropped further, we had to move fast. We identified those who needed help most. As we worked, an old man died in front of us from the cold.

No medicines. No heating, No fuel to cook the food.

I checked a few nearby buildings to see if there were any other people. There weren't.

But there was another body. We could see it, but it was trapped under a collapsed building. We couldn't do anything about it.

The horror of this scene is but a snapshot of conditions across many of Syria's urban battlefields. For months, aid agencies and medical workers have known about the hardships endured by civilians trapped in besieged rebel areas, deprived of food and basic medical supplies. But they have not been able to reach them. Residents in Madaya, a rebel-held town outside of Damascus, say their last hospital is no longer in operation and that many are suffering from severe malnutrition. Save the Children recently reported that the state of distress is so severe for some young people that there has been an upsurge in suicide attempts among teenagers.

“This is not about who is right, or who is wrong. Who is winning, who is losing,” the Red Cross worker wrote to the BBC. “This is about people: flesh and blood, human beings. Bleeding, dying, being made orphans, every day.”

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