Since last October, the evidence has mounted that Israel is executing a genocide in Gaza. Genocide has a precise meaning in international law: the intentional destruction of a people, “in whole or in part”. The legacy of the Holocaust makes us think of “genocide” as the ultimate term to describe an atrocity of this kind. Yet there are limits to using this legal term alone to explain and express the immorality of what is going on in Gaza. To me, no legal concept or criminal offence can fully fathom the horrors of Gaza. It is more than genocide – it’s gleeful killing without restraint.

I am referring here, above all, to the celebratory manner in which Israeli soldiers record their destructiveness in Gaza on their smartphones, a practice so pervasive as to have caught the attention of even mainstream outlets usually reluctant to scrutinise Israel intensely, such as the Washington Post (of course, pervasive doesn’t mean ubiquitous – some Israeli soldiers hesitated over rather than revelled in killing). It is one thing to kill children in front of their families, destroy and desecrate holy places, pillage even the means of survival like food and clothing. But then to boast and joke about it?

The modern laws of war and modern military discipline revolve around the notion that with proper training, including instruction in humanitarian law, soldiers can carry out orders to destroy and kill while exercising professional restraint. They can be as lethal as is needed to accomplish military goals while acting in accordance with a moral, and legal, code.

As we now see with Afghanistan and Iraq, the psychic cost to soldiers of balancing these demands is enormous – PTSD seems to be the rule, not the exception. We also know that some soldiers snap on the battlefield, spontaneously going on a rampage and leaving all restraint behind them. Others do not.

Ford Madox Ford, a writer who experienced the trenches of the first world war, has the narrator in one of his short stories put it this way: “There were many who went over the edge of unreason—but there were many who stayed, by the grace of God, just on this side of the edge.” Conscience and war are not as such incompatible. “Are we beasts? Have we gone too far?” Winston Churchill asked when he was about to give the orders to bomb civilian areas in German cities. Later he shed tears for the innocent victims of his own war strategy.

Now what of Israel’s leaders? As South Africa documented in the first stages of its genocide case against Israel at the International Court of Justice, Israel’s military and political leaders repeatedly told their soldiers to destroy everything, to remove every restraint – an invitation to go over the edge, in Madox Ford’s words.

This is not just about genocide. It is also about legicide – destroying the whole notion of legal limits in war – as well as the mass destruction of the moral lives of soldiers, their souls and consciences.

The perverted joy of killing did not begin in Gaza. According to the German philosopher Friedrich Nietzsche, ancient societies knew “the sheer satisfaction of being able to wield, without a scruple, power over one who is powerless … the great joy and delight [of cruelty]”. “Without cruelty,” Nietzsche wrote, “no feast”.

This ancient human tendency to cruelty has never been expunged from the human condition, even after several genocides and two world wars. There are the unforgettably horrific photos from Abu Ghraib – US soldiers smiling in selfies with the corpses of detainees tortured to death by the CIA. As the recent Canadian thriller Red Rooms – about a fictional man alleged to have broadcast his murder of three teenage girls to a dark web chat room – reminds us, this exists even without the conditions of war. Gleeful killing recurs throughout human history, and however grave a charge, genocide does not encapsulate it (nor even necessitate it – to Hannah Arendt, Eichmann represented the banality of evil).

What drives Israeli soldiers to such evil? Perhaps the Nietzschean pleasure trip of eliminating the powerless – though perhaps other things, too. Jack Saul, a trauma therapist and scholar who has examined the moral injury that wartime violence does to soldiers, has pointed out soldiers’ need to show one another that they are strong, up to the awful task given to them – that they can “keep it together”. This could explain some of the smiling selfies in front of destroyed homes, hospitals, schools and mosques: a desperate attempt to suppress moral injury, to deny that your crimes are destroying you from the inside.

In a letter to the German philosopher Karl Jaspers around the time of the Eichmann trial, Arendt wrote that crimes of genocide “explode the limits of the law and that is precisely what constitutes their monstrousness”.

In calling out genocide today, it is both legally and morally correct to emphasise the people of Gaza as the main victims. Yet the harm to law and morality done by Israel extends beyond them – it has wrought a moral abyss that has no legal name. International humanitarian law, to be sure, has legal offences that reach practices such as the humiliation of victims, and affronts to their human dignity. Some of what we see on the Israeli soldiers’ smartphones likely amount to that. Sentencing in international tribunals can take account of the attitude with which soldiers kill, to an extent – “aggravating factors” include “particular cruelty”. But none of this completely or exactly captures the breakdown of morality represented by those selfies and the acts they document with exhilarating joy. Not only the Palestinian people will require recovery from this genocide – this more than genocide – but humanity itself.

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