As the recent terrorist attacks in Paris and San Bernardino show, Islamic State has achieved a global reach. No longer satisfied with terrorising large swaths of the Middle East, it is inspiring, recruiting, training and supplying terrorists to carry out murderous acts around the world.

Given this new international agenda, analysts are struggling to assess the source of the group in an attempt to improve their understanding of how to stop it. In terms of its source, most point to Saudi Arabia; in terms of stopping it, most point to the United States. However, a closer look at Isis reveals that it is engaged in an entrenched theological war with the Saudi religious establishment to determine who justifiably espouses the purest tenets of Sunni Islam. As the custodian of the two holy mosques in Mecca and Medina and the host of the world’s Muslims for the pilgrimage, Saudi Arabia leads one and a half billion Muslims in fighting Isis. The kingdom’s leadership of the recently announced Muslim coalition to fight terrorism in all its forms confirms that Saudi Arabia is not only not the source of Isis but it is the terrorist group’s central opponent and the only nation that can fully and legitimately defeat it once and for all. More than 34 countries have joined the coalition.

Three factors clarify Saudi Arabia’s intrinsic and total war on Isis. First, many people claim that Saudi Arabia is the source of Isis because both practise a version of Islam called Salafism (erroneously known in the west as Wahhabism). Salafism is rooted in the word salaf, or “forefathers”, and refers to the way the prophet Muhammad’s followers in the religion’s first three generations practised Islam. And while it is true that the kingdom espouses Salafism, Isis’s claim that it is Salafi has no theological basis, because the group is in fact a continuation of a crude sect known as the Kharijites, or the ones who “defected” from the Muslim community (ummah) during the reign of the fourth caliph Ali (whom the Kharijites assassinated). The Kharijites, like Isis, believe that whoever disagreed with them should be murdered as infidels (takfir), rationalised mass killings against civilians including women and children (isti’rad), and practised an extreme form of inquisition to test their opponents’ faith (imtihan).

Isis’s adherence to the Kharijite ideology is not the only reason it is not a true Salafi movement; it has also committed an act of disobedience that effectively nullifies its Salafi pretenses. In original Islamic scriptures and practice, the highest authority is the “guardian” of the ummah, (wali al amr). All religious, political and military powers are concentrated under this authority, which Saudi Arabia’s system best exemplifies in the modern world. In other words, King Salman’s legitimacy to rule is contingent on him being first and foremost the wali al amr of the people, and in return the people show their acceptance of his rule by proclaiming him as their ruler. This proclamation (bay’ah) is a contract between the ruler and the ruled in which the first swears to promote Islam and the welfare of the second, and the second swears to obey (ta’ah) the tenets of Islam and follow the first’s leadership. Should the first deviate from Islam, the second is obliged to replace him. The joint bay’ah of the ummah to the ruler is fundamental to Salafism and anyone that breaks the bay’ah – as Isis has done – can never again be considered a true Salafi.

Given the importance of the wali al amr to Sunni Islam, Isis and Saudi Arabia are locked in a theological struggle from which only one can emerge victorious.

The second reason Saudi Arabia and Isis are in complete opposition is that the core mission of Isis is to restore the caliphate, an Islamic empire led by a supreme leader. Given that the kingdom is the epicentre of Islam, Isis’s road to the caliphate lies through the kingdom and the Saudi people. Isis has conducted a series of terrorist attacks in the kingdom in the past year. In response Saudi Arabia has put the group on its list of terrorist sponsors, declared that belonging to or funding Isis is a crime punishable by death and arrested countless Isis supporters, operatives and financiers.

The final reason why Saudi Arabia is Isis’s strategic enemy is financial. As an organisation with expanding ambitions, Isis requires ever-expanding resources. Therefore, just like al-Qaida, Isis covets the kingdom’s enormous oil fields and monetary wealth.

When Isis first appeared in Syria in 2011, Saudi Arabia tried to galvanise support for the moderate Syrian opposition. But the world failed to listen. Now Isis is a threat not only to the Middle East but also to the entire world. Only a coalition led by Saudi Arabia can genuinely defeat Isis while also delegitimising the group in the eyes of the wider Muslim world. If the nations of the world hope to completely defeat Isis, they should stop falsely accusing the Saudis of creating the group and instead join them in defeating it.

• This article was amended on 22 December 2015 and again on 24 December 2015 to clarify Nawaf Obaid’s role as a former communications adviser to the Saudi government. This article is written in a personal capacity.

