The religious diplomacy of Saudi Arabia constitutes a strange black hole in the analysis of radicalism that affects Islam and the Middle East today. Why has Salafism, the most intolerant and sectarian movement of Islam, become so prevalent? Of all the religious radicalisms that rot the planet, it is the only one to enjoy the constant support of a country endowed with immense means: the Saudi kingdom.

This study, whose collaborators wanted to remain anonymous, reveals how the two sides of the kingdom – the conciliatory one of the Saud dynasty and the more aggressive Salafism, propagandist of jihad – has for decades developed a religious strategy to conquer the Muslim community and the West without appearing as an enemy. One of the most striking examples is the absence of sanctions or even accusations by George W. Bush towards Saudi Arabia in the aftermath of the September 11th attacks even with fifteen identified Saudis among the terrorists.

The...