The jihadist manual behind the brutality that underpinned Islamic State has been revealed for the first time in new analysis of a 579-page text, written by the Isis ideologue Abu Abdullah al-Muhajir.

The text attempts to legitimise the barbarous acts of the jihadist group, including the mutilation of corpses, the trade in human organs, beheading, the killing of children along with “scorched earth operations” and global terrorist attacks.

After two years examining and transcribing the document, experts at the counter-extremist group Quilliam have completed a meticulous appraisal of the extremists’ core textbook along with a robust theological rebuttal of its “twisted” interpretation of Islamic teachings. Used by Isis and its supporters to validate a large range of horrific acts, the “bible for jihadists” provided the theoretical and legal framework for the violent terrorist group.

“There is a startling lack of study and concern regarding this abhorrent and dangerous text in almost all western and Arab scholarship,” says the report. “We hope to expose and deconstruct this unprepossessing yet deeply insidious and pernicious text.”

Known as the Fiqh al-Dima (or The Jurisprudence of Blood), the book is the key Salafi-jihadist text. It attempts to justify the use of weapons of mass destruction, perpetrating genocide, the murder of non-combatants, the taking of sex slaves and hostages.

Researchers for Quilliam managed to acquire a copy of the manual online in 2015, after researchers spotted the Fiqh al-Dima being used to teach new recruits to Isis’s caliphate in Syria. Back then, Islamic State’s self-styled caliphate encompassed vast swaths of Syria and Iraq and a population of up to eight million. Since then the group has lost 98% of territory in the two countries and is now largely confined to a strip of desert straddling the Iraqi-Syrian border.

The manual offers the group guidance on “military retreat” with a chapter devoted to “surrender vs fighting to the death” that says jihadists should choose death instead of handing themselves over to the enemy.

However, Sheikh Salah al-Ansari, a senior Quilliam researcher who translated the manual from Arabic and wrote the rebuttal, said no religious requirement existed to “fight to the death” and that the Islamic tradition of warfare encouraged the humane treatment of prisoners of war. “Our work comprehensively debunks and rejects Isis’s proto-Islamic arguments, demonstrating their ignorance and disregard for traditional Islamic scholarship as well as for the basic humane and Islamic values of mercy and compassion,” said Ansari.

The titles of the text’s 20 chapters include “Beheading, decapitation and mutilation”, “Kidnapping warring infidels” and “How to kill spies”.

Another chapter, titled “Indiscriminate killing of warring infidels”, opens with an inflammatory message that calls for force to be used against unbelievers: “Kill them, fight them by every means that may snatch away their souls, drive their spirits from their bodies, cleansing the earth of their filth and removing their scourge from mankind, whatever that means may be.” A separate chapter documents attempts to justify the use of weapons of mass destruction. “The central aim for which we strive – and we do so with all available strength – is the acquisition of weapons, weapons of mass destruction, for there is no escaping the obligation to defend against these defiant perverters of faith and end the aggression of the malodorous filth against Islam and its people,” writes Muhajir, the Isis author.

A vulnerable reader who has no previous training in Islamic jurisprudence might easily become seduced by this book Sheikh Salah al-Ansari

Each point he makes is theologically rebutted by Quilliam using the Qur’an, Islamic teachings and reference to acts prohibited by Islamic warfare ethics and Islamic morality. “This text offers intricate details on the use of jihad in its traditional Sunni discussion, and misuses these features to provide Islamic legal cover to terrorist operations,” said Ansari.

Among one of its central strands is the distinction between the “lands of Islam” and the “lands of unbelief (kufr)” and the notion that jihadists are entitled to fight the unbelievers.

“This entire binary construct is a later invention of Muslim theologians that is now obsolete, and so the justification of excommunication (takfir) and military attacks against civilians on this basis is completely absurd,” says the Quilliam report. Even so, Ansari said history had proved that some were swayed by the text, even chapters 11 and 12, which attempt to provide an Islamic sanction for the mutilation of bodies, the cutting of body parts and beheading.

“A susceptible and vulnerable reader who has no previous training in Islamic jurisprudence might easily become seduced by this book because it is written in a way that gives the impression that it has religious weight. While the text is somewhat based on traditional readings, it does not reflect the diverse and pluralistic complexities of Islamic rulings,” said Ansari.

The jihadis’ interpretation of jihad – the text has also been used by al-Qaida and Nigeria’s militant Islamist group, Boko Haram, to justify and commit atrocities – would have been core teachings to Isis’s 6,000 European Muslims who travelled to the calpihate, of which about 850 were British.

“They would have been introduced to this book, it is their bible, their most important text,” said Ansari.