It is hard to describe the cumulative effect this devastating chronicle has over 280 pages. It describes a mounting toll of death and destruction, with each day bringing more heartrending news of homes demolished and relatives and colleagues killed. Gradually, it makes it clear that there is no safe place in the Gaza Strip. Danger is everywhere, like the low hum of a mosquito.

Atef Abu Saif is an acclaimed Palestinian author and journalist as well as being minister for culture in the Palestinian Authority. On 7 October he found himself in Gaza purely by chance. He was due to speak at a cultural event in Khan Younis to celebrate Palestinian Heritage Day, but found himself instead at the centre of a war.

Abu Saif lives with his own family in the West Bank, but he and his wife grew up in Gaza. He had travelled there ahead of time with his adolescent son, so that they could see grandparents, relatives and friends. In the event, he was there for 85 agonising days before, in desperation, he and his child made their way to the Rafah crossing and from there back to Ramallah.

Few who read this will have direct experience of war; we are among generations in the west that have been blessed to live without conflict. That is why we are duty‑bound to place ourselves in the shoes of those who do suffer these horrors, especially when our governments supply the armaments that make war possible. Abu Saif would say ruefully that his people, the Palestinians, have lived through 75 years of war, starting with displacement and forced exile and then the denial of self-determination and a secure homeland. War has stalked his grandparents’ lives, those of his parents and now his. The wisdom of experience is passed on: “When bombing starts, move to the middle of the building, a corridor or stairwell … the most fortified part of the building.” Or, chillingly: “Don’t stay together. Sleep in different places. So that if part of the family is killed, another part lives.” But nobody in Gaza really knows how to keep safe.

Abu Saif’s diary records increasing attacks from sea and air; the drones, the flashes of light before explosions; the nights spent counting bombs and, if sleep comes, the nightmares of bleeding children. He tells us of the bombing of hospitals where people had taken sanctuary, the bombing of churches and mosques, schools and universities. Electricity is cut off. He explains how notices fall from the sky saying in Arabic that anyone who remains north of the stream that bisects the Strip will be regarded as partnering with a terrorist organisation. They are to move south. But Abu Saif knows that this will be no guarantee of security. The day before, friends who had followed the orders were killed in missile strikes as they moved slowly in traffic on the southbound road. They had obeyed other orders to move twice before. Move on. Move on. And what then? Move out?

Abu Saif joins chains of men, lifting pieces of concrete and passing them along, desperate to find life under the rubble. The son of a cousin wanders the streets calling for his children by name, believing they might still be alive after his house was blown up. His howls of grief are unbearable, and Abu Saif tries to block out his lament. People we have come to know in the early days of the journal are lost too, killed in overnight bombardments or in efforts to escape the advancing army.

Food, fuel and water run out, as do medicines and bandages. There are no painkillers or sedatives. The wounded are operated on without anaesthesia. Abu Saif makes no pretence of bravado and describes his own fear of death. “I heard its steps growing louder and louder. I saw its jaws open, as it grew closer. Just be done with it, I thought.”

And then, Abu Saif’s sister-in-law, his wife’s only sister, Huda, her husband and most of their family are killed in a missile attack – civilians living ordinary lives, blown to smithereens in their own home. He cannot bear telling his wife. He goes to what is left of the house with his father-in-law and searches through the rubble as the old man weeps. The only survivor is Wissam, one of the daughters, who had just graduated from art school. Atef finds her in a hospital, both her legs amputated and missing her right hand. She is delirious, dreaming an awful dream that her limbs have gone, but it is horribly real.

The people of southern Israel undoubtedly suffered terrible atrocities on 7 October 2023 at the hands of Hamas. However, we have to be capable of holding two truths in our hearts. What is happening to the people of Gaza is also deeply horrifying. Three principles underpin the law of armed conflict: the distinction between combatants and civilians, proportionality, and the obligation to take appropriate precautions to minimise civilian harm. Is this a genocide? The international court of justice (ICJ) will decide that issue in the fullness of time. Meanwhile, under the genocide convention, the world is expected to prevent such a trajectory. The ICJ has given a warning to Israel; now is the time for all of us to say: enough is enough. As Abu Saif’s account so vividly shows, this war has to stop, and a truly just peace must be secured.

• Helena Kennedy KC is a barrister and member of the House of Lords. Don’t Look Left: A Diary of Genocide by Atef Abu Saif is published by Comma Press (£11.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.