I don’t think that in all my years of doing this I’ve ever seen such dreadful pictures of injuries, of people lying on the floor of an emergency room, the dead mixed with the living.

One colleague, who I speak to all the time, was in despair, sending me all these photographs, and saying: “David, you have to do something to help us.” But what can I do?

The message out of eastern Aleppo is that there are no hospitals functioning at all. They have all been repeatedly attacked in the past few days. Some were able to evacuate, but one was totally and utterly destroyed by rockets and bombs. I heard that two doctors were killed and 16 other staff injured and I am afraid that one of the dead may be a brilliant surgeon, who would be a particularly serious loss.

There is another hospital that we haven’t even had a message from. So, I suspect they are out of action, but we know nothing about the staff or the conditions there.

The Aleppo hospitals have been re-opened so many times, underground or at new locations, but between the bombing and the siege I don’t know if it will be possible to resurrect them this time. There is so much equipment that you need in order to operate and there is no sterilisation and no monitoring machines for anaesthetics. Even if the hospitals saved some machines they can’t run them because the generators have been destroyed or are out of fuel.

The taking out of every hospital and medical facility that gives hope and help to civilians is not a coincidence. The medics have such fantastic morale that you would not imagine them giving up, but I have an awful suspicion that this is the endgame.

My colleagues in Aleppo were warning me a week ago that “now is the time to do something”. Their phones had been blitzed by text messages from Assad’s government and the city was showered with leaflets that said: “If you do not leave in the next 24 hours you are going to be killed.”

Syrians comfort each other on 19 November, following a reported air strike on Aleppo’s rebel-held neighbourhood of Bab al-Nayrab. Photograph: Ameer Alhalbi/AFP/Getty Images

I tried my best to raise the alarm, but everyone outside Aleppo brushed it off as propaganda. Then the attacks began, and it’s been a constant, unbearable barrage of every kind of weapon. One colleague said they had counted 1,700 individual attacks; everything from barrel bombs with chlorine to huge, devastating missiles.

My friends say they will not leave because they have no guarantees of safe passage, but if they do not leave I am afraid they will die. Nobody is going to stand up to Assad and the Russians, and we saw in Grozny in 1994 what they are capable of.

Someone, somewhere needs to fly a white flag and say: “We will go in and get these people out.” The civilians and doctors must be taken out to safe areas in the north of Syria. Some areas are relatively demilitarised, hospitals are functioning, you could set up a no-fly zone or a no-bomb zone and get the UN to set up a refugee camp.

It’s the first time I’ve really felt that its not going to work any more. All of us have tried our best, every person involved in helping the doctors keep it all going. But there is a time when you have to realise that, no matter what you do, the odds are against you.

Over the past three months I have spoken to every media outlet and politician I could reach, pushing for Russia to be held accountable for what is happening, but there was no response.

So, I find it utterly, utterly tragic that we see this unfolding today, because it was so clear what was coming and nothing was done to stop it.