Back in Afghanistan, the mind turns to the small matter of savagery. Not the routine cruelty of war but the deliberate inhumanity with which we behave. The torture and killing of prisoners in this pitiful place – the American variety in Bagram and the Taliban variety in Helmand – is a kind of routine of history. Even execution has to be made more painful. A knife is more terrible than a bullet. The cult of the suicide bomber in the Middle East began its life in Lebanon, moved to "Palestine", arrived in Iraq, leached over the border here to Afghanistan and passed effortlessly through the Khyber Pass into Pakistan. And New York. And Washington. And London...

Are human beings at war – any kind of war – by definition bound to commit atrocities? The International Committee of the Red Cross tried to answer this question in a report four years ago. Were combatants unaware of international humanitarian law? Unlikely, I would think. They just don't care. The Red Cross enquiry interviewed hundreds of fighters in Colombia, Bosnia, Georgia – a bit of real prescience, there, on the part of the ICRC – and the Congo, and suggested that those who commit reprehensible acts see themselves as victims, that this then gives them the right to act savagely against their opponents. Certainly, this might apply to the Palestinian-Israeli conflict, very definitely to the Serbs of Bosnia – I'm not so sure about Georgia – and quite definitely to the Taliban (not least when we've been bombing more wedding parties).

Such cruelty is abetted with a bodyguard of clichés – "police operations", "clean up", "mop up", "surgical strikes" – where you can kill by remote control, "especially when the media are not present to show the realities of a conflict". This is most certainly the case today, for what journalist will now dare to wander the village streets of Helmand or the city of Baquba in Iraq or, for that matter, the border towns of Pakistan? War has never, it seems, been so underreported. And both the good guys and the bad guys like it that way; they prefer to indulge in savagery unseen.

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There is nothing new in all this. At the Battle of Omdurman – where the British executed all the Arab wounded – the young Winston Churchill wrote of a sight which is familiar today in a land which was then called Mesopotamia and in another which was already called Afghanistan. He described "grisly apparitions", of "horses spouting blood, struggling on three legs, men staggering on foot, men bleeding from terrible wounds, fish-hook spears stuck right through them, arms and faces cut to pieces, bowels protruding, men gasping, crying, collapsing, expiring...". To the men can now – this very week – be added the suicide-bombed schoolgirls of Baghdad.

In his earlier military campaign on the North West Frontier, Churchill saw how some of the Taliban's ancestors dealt with a wounded British officer: the leader of "half a dozen Pathan swordsmen ... rushed upon the prostrate figure and slashed it three or four times with his sword. I forgot everything else at this moment except a desire to kill this man. I wore my long cavalry sword well sharpened... The savage saw me coming...". Well there's something for the ICRC to think about.

Yet it pays to remember that Afghan wars have always been dreadful. Sir Mortimer Durand – he who created the Durand line which masquerades as the Afghan-Pakistani border, crossed with such impunity today by Americans and Taliban warriors in order to kill each other – witnessed the cruelty of the Afghan war at first hand. "During the action in the Chardeh valley on the 12th of Dec 1879," he wrote, "two squadrons of the 9th Lancers were ordered to charge a large force of Afghans in the hope of saving our guns. The charge failed, and some of our dead were afterwards found dreadfully mutilated by Afghan knives... I saw it all..."

Yet Durand himself objected profoundly to a statement from General Frederick Roberts – he of Kandahar fame – after the murder of the British mission diplomats in Kabul. The killings had been "a treacherous and cowardly crime, which has brought indelible disgrace upon the Afghan people... all persons convicted of playing a part in (the murders) will be dealt with according to their deserts". Durand confronted Roberts over this Victorian version of the message that George Bush would give to the Afghans 122 years later.

"It seemed to me so utterly wrong in tone and in matter," Durand would later write, "that I determined to do my utmost to overthrow it... the stilted language, and the absurd affectation of preaching historical morality to the Afghans, all our troubles with whom began by our own abominable injustice, made the paper to my mind most dangerous for the General's reputation."

Of course, it did Roberts no harm at all. In the age of "shock and awe" – when a Canadian general can call his Taliban opponents "scumbags" – it still doesn't seem to worry Nato officers. They should know better. Montgomery never cursed Rommel; he kept a photograph of the Afrika Korps commander in his caravan to remind him of the man he was fighting. But then again, didn't Montgomery fight in the age of the Holocaust, of industrial killing, of the Hamburg and Dresden firestorms? Indeed, the very Geneva Conventions of 12 August 1949 were supposed to end the mass destruction of human life. And President Bush has torn them up.

I know it's easy to ridicule the Red Cross. There's something very preachy about the post-war conventions. But apart from the precedents of international law, it's all we've got. Maybe a million Pushtu-language editions should be handed out to the Taliban and their followers as well as to the Nato combatants whom Barack Obama absurdly believes will win the Afghan war. But I doubt it would do much good. Victimhood sits easily on all our shoulders. If Osama bin Laden had a conscience, it would be quickly eased by the destruction of the last Caliphate, the colonial occupation of the Muslim world, the deaths of millions of Arabs. And if we have a conscience, what do we say? Remember 9/11. And so on we go.