laws (royal decrees). The ulama have also influenced major executive decisions, for example the imposition of the oil embargo in 1973 and the invitation of foreign troops to Saudi Arabia in 1990. It plays a major role in the judicial and education systems and has a monopoly of authority in the sphere of religious and social morals. By the 1970s, as a result of oil wealth and the modernization of the country initiated by King Faisal, important changes to Saudi society were under way and the power of the ulama was in decline. However, this changed following the seizure of the Grand Mosque in Mecca in 1979 by Islamist radicals. The government's response to the crisis included strengthening the ulama's powers and increasing their financial support: in particular, they were given greater control over the education system and allowed to enforce stricter observance of Wahhabi rules of moral and social behaviour. Following his accession to the throne in 2005, King Abdullah took steps to rein back the powers of the ulama, for instance transferring their control over girls' education to the Ministry of Education. The ulama have historically been led by the Al ash-Sheikh, the country's leading religious family. The Al ash-Sheikh are the descendants of Muhammad ibn Abd al-Wahhab, the 18th century founder of the Wahhabi form of Sunni Islam which is today dominant in Saudi Arabia. The family is second in prestige only to the Al Saud (the royal family) with whom they formed a "mutual support pact" and power-sharing arrangement nearly 300 years ago. The pact, which persists to this day, is based on the Al Saud maintaining the Al ash-Sheikh's authority in religious matters and upholding and propagating Wahhabi doctrine. In return, the Al ash-Sheikh support the Al Saud's political authority thereby using its religious-moral authority to legitimize the royal family's rule. Although the Al ash Sheikh's domination of the ulama has diminished in recent decades, they still hold the most important religious posts and are closely linked to the Al Saud by a high degree of intermarriage. Corruption Corruption is widespread in Saudi Arabia, most prevalent in the form of nepotism, the use of middlemen, ‘wasta’, to do business as well as patronage systems. The Saudi government and the royal family have often, and over many years, been accused of corruption. In a country that is said to "belong" to the royal family and is