Israeli historian Benny Morris doesn’t do things by half. The footnotes of his new book on the 30-year genocide of Christians by their Turkish rulers, cowritten with his colleague Dror Zeevi, take up more than a fifth of the 640-page work. “It was nine years, a long haul,” he admitted to me this week, with an audible sigh over the phone. And he talks about the involvement of Ataturk in the later stages of the genocide of around 2.5 million Christians of the Ottoman empire; how “religions do drive people to excessive violence” – he has in mind the Turks, Isis, the Crusades – and even condemns the Arabs for their inability to criticise themselves.

The mere title of the Morris-Zeevi book, The Thirty-Year Genocide: Turkey’s Destruction of Its Christian Minorities 1894-1924 (to be published by Harvard University Press in April) is going to have the Turks enraged, from Erdogan down. The Armenians and other Christians will dispute his apparent claim that he has only just discovered that their slaughter lasted for 30 years – others have talked of the Armenian genocide of 1915 bookended by the late 19th-century massacres in Turkey and the post-1915 killing of surviving Armenians and Greeks, Assyrians and others. And the Arab world will challenge his view that the holocaust (my word) of Christians was more motivated by Islam than Turkish nationalism.

Having written about the genocide of the Armenians for 35 years, I have doubts that the actual call for “jihad” in the Turkish Ottoman empire unleashed at the start of the First World War was as ferocious as Morris makes it out to be. Muftis were indeed told they were in a holy war against Christians – but not against German Christians, Austro-Hungarian Christians, neutral Christians or allies of the Central Powers (Bulgaria, for example). Many Muslim worshippers, sitting on the carpets of mosque floors, must have shaken their heads in puzzlement at these caveats. Well, one way was to notice the German officers training the Ottoman army, the German diplomats and businessmen who witnessed the genocide of the Armenians with their own eyes, and wrote home about it. Hitler asked his generals who now remembered the Armenians just before invading Poland in 1939.

But again and again, I was brought up short by the sheer, terrible, shocking accounts of violence in Morris’s and Zeevi’s work. “Strident religiosity” moved through the Muslim lands, write the authors.

The date: 1895. The place: Severek. The witness: Armenian survivor Abraham Hartunian. “The first attack was on our pastor [Mardiros Bozyakalian]. The blow of an axe decapitated him. His blood, spurting in all directions, spattered the walls and ceiling with red. Then I was in the midst of the butchers. One of them drew his dagger … Three blows fell on my head. My blood began to flow like a fountain … The attackers [were] sure that I was dead … Then they slaughtered the other men in the room, took the prettier women with them for rape …”

Now it is July 1915. The place: Merzifon. The witness: missionary JK Marsden. “They were in groups of four with their arms tied behind them and their deportation began with perhaps 100 … in a batch … they were taken about 12 miles across the plains, stripped of their clothing and, in front of a ditch previously prepared, were compelled to kneel down while a group of villagers with knives and axes quickly disposed of them. For a week, this was repeated until 1,230 of the leading Armenian men had been disposed of.”

Armenians mark 101 years since genocide Show all 10 1 /10 Armenians mark 101 years since genocide Armenians mark 101 years since genocide Armenian people carry torches during a march to commemorate the mass killings of Armenians Getty Armenians mark 101 years since genocide Armenian people take part in a march in commemoration of the 101th anniversary of the mass killings of Armenians by Ottoman forces in 1915 Getty Armenians mark 101 years since genocide People hold a flag during the laying of the flowers at the Genocide Memorial in Yerevan Getty Armenians mark 101 years since genocide President Serzh Sargsyan and actor George Clooney attend the laying of the flowers at the Genocide Memorial in Yerevan Getty Armenians mark 101 years since genocide Armenian clergymen, US actor George Clooney, center, Armenian President Serzh Sargsyan, second right front, and guests attend a ceremony at a memorial to Armenians killed by the Ottoman Turks, in Yerevan AP Armenians mark 101 years since genocide Armenian President Serzh Sarkisian (C,R) and US actor George Clooney (C) attend a ceremony at the Genocide Memorial in Yerevan Getty Armenians mark 101 years since genocide A general view of attendees and mount Ararat during the laying of the flowers at the Genocide Memorial in Yerevan Getty Armenians mark 101 years since genocide Lebanese of Armenian descent burn an effigy of Turkish president Erdogan during a protest in front the house of Turkish Ambassador to mark the 101st anniversary of the mass killing of Armenians in the Ottoman Empire in 1915, near Beirut, Lebanon EPA Armenians mark 101 years since genocide Activists hold portraits of victims during a silent demonstration to commemorate the mass killings of Armenians by Ottoman Turks in Istanbul Reuters Armenians mark 101 years since genocide Activists hold portraits of victims during a silent demonstration to commemorate the mass killings of Armenians by Ottoman Turks in Istanbul Reuters

In January 1920, YMCA secretary CFH Crathern was in Marash. The wife of an Armenian pastor had reached his hospital. “She was bleeding … from three bullet and three dagger or knife wounds while a child of 18 months had been taken from her breast and slain with a knife, and an older girl killed with an axe. To add to the sorrow of it, this woman was pregnant and had a miscarriage as soon as she reached the hospital.” The woman died the following day.

I have repeated above only a few of the less bloody episodes from the 30 years. I will spare readers the chopped off fingers, the thousands of raped girls, the priests beheaded or burned on crucifixes.

In the final annihilation of the Armenians, an American missionary spoke of “minds obsessed with Muslim fanaticism seven times heated”. Turks, he wrote, had “become drunk with blood and rapine, and plunder and power, and he will be a different man from what he was before the atrocities”. Benny Morris thinks it was more to do with a mixture of modern nationalism and the decline of “Islamic polity”.

I discussed all this with him. Is it possible for a people to be so inured to cruelty that they changed, that their acts of sadism could alter their humanity? Religions drive people to excessive violence, he said again, and then repeated this as “excessive sadism”. Morris agreed that the Romans were cruel, but they were pagans. “In terms of religion, the Romans were amateurs. Abrahamic religions drive people to excess.” Jews had avoided this. Palestinians will disagree.

There is certainly a frightening geographical scope to the killings. Many thousands of horrors were perpetrated in Mosul, Raqqa, Manbij and Deir ez-Zor, names grimly familiar from the Isis torments of 2014 onwards.

Why, one keeps asking, didn’t the Christians leave after 1924? But of course, they had been urged to return to settle in Cilicia and in Mesopotamia and Syria by the French and British – who left; and thus the Christian descendants waited for the next generational bloodletting.

The Turks were not the only killers, and Kurds also killed the Christians for the Turks, as Ukrainians killed the Jews for the Nazi Germans. At one point in Morris’s text, a group of Circassians plait a rope 25 yards long from the hair of young women they have killed, and send it as a present to their commander.

Mustafa Kemal Ataturk gets pretty well trashed in this volume. “There are accounts of him saying in 1922 that, ‘Our aim is to get rid of the Christians’ – he said this in a number of conversations,” Morris contends. “He gave orders, and men in his later government were responsible.” But if this 30-year history of blood was fuelled by “Muslim fanaticism”, there are “good Turks” in the book. In the first massacres, government officials arrested Essad Bey, an “honest, impartial and tolerant” judge who tried to help the Christians. There is a heroic Turkish doctor who throws out his sick Turkish soldiers from a hospital and replaces them with Armenian refugees. Missionary Tacy Atkinson hoped to meet the doctor one day “in the Kingdom of Heaven”. There are others. It’s true that the Greek Christians have fewer historians than the Armenians. Tens of thousands of Greeks were transported to Greece in return for an equal number of Muslims – official agreements kept the massacres a trifle smaller – but Morris and Zeevi give too little attention to the awe in which the Nazis held Ataturk’s people.

Ataturk himself cared little for Islam: he smoked and womanised, and was a nationalist before he was a Muslim. The Nazis admired his “Turkified” non-minority republic. When he died, the front page of Volkischer Beobachter was fringed in black.

The authors briefly compare the Jewish Holocaust and the Armenian genocide – I prefer the terms Jewish Holocaust and Armenian Holocaust – and there are some already published parallels. Armenians might be spared if they would convert to Islam or marry Muslim men. Jews could not save their lives by converting. The Turkish massacres were more sadistic. I rather think the German-inspired slaughter could be just as bad in the Second World War: witness the head-chopping at the Jasenovac camp on the Croatian-Bosnian border. Persecution of the Jews under the Nazis lasted at most 12 years, but persecution of Christians in Ottoman territories 30 years.