There’s a very good reason why For Sama has been classified as 18. It is probably one of the most distressing, emotionally challenging films I have ever seen. It leaves nothing to the imagination. It is uncompromisingly harrowing for much of its running time though threaded with hope.

Newly arrived at the city and university Waad al-Kateab picks up her mobile and films her early days at Aleppo University in 2012 as the students protest against the Bashar al-Assad regime. Taking in her friends as they actively oppose the regime with some optimism. It then becomes a chronical of despair and cruelty as the regime brutally tightens its grip around the city, eventually turning into a full-blown attack and siege.

In all this Waad meets and marries a young medic Hamza and together with their friends and colleagues manage to actually get a hospital up and running on the most meagre of resources and surrounded by the most violent and indiscriminate of attacks. The images of them pulling together with the commentary that some of those friends and colleagues didn’t survive are filled with pathos.

Those who do are forced to pull on every resource to help the causalities as they arrive at the hospital, which becomes a charnel house. Brothers taking their sibling in for him to be pronounced dead. The dead and the dying in the hospital caked in blood and grime as the regime relentlessly continues its oppression. Horrific scenes of bodies pulled across floors leaving trails of blood, and a distraught mother taking their dead child out of the hospital for burial. The CCTV footage of a shell hitting the site; the walls and people, just disappearing requires no other words.

But there is some relief with the type of black humour that can only be really understood by those there. There’s the intimacy of Waad and Hamza’s wedding, their move to their new house, playing in the snow. And of course, the birth of Sama; a beautiful gleam of hope and innocence. There are opportunities for them to leave the city, forgoing them to stay on and struggle on for what they see as the higher principles of freedom.

When the Russians get involved the attacks take on another level of ferocity with the use of gas, cluster and barrel bombs. With only one hospital and three hundred casualties a day the odds are impossible.

Eventually it just becomes too much and in 2016 they are forced into exile that in itself uncertain as Hamza – a well-known face – could be stopped at the border.

Co-directed Waad and Edward Watts the film is by and large chronological using Waad’s footage that she filmed and managed to smuggle out of Syria. Her initial idea was just to capture the protests then as things started to escalate it was a matter of capturing the raw images of the siege; the devastation, tragedy and poignancy of the situations, for Sama. In that Waad is utterly successful.