The Saudi kingdom can be considered one of the youngest of the oldest kingdoms in the world. Its establishment and operation recalls the reign of the Spanish Catholic monarchy of the 15th century. Similar to the Ferdinand and Isabella pact with the Catholic church to gain recognition for their kingdom in return for sole approval of the Catholic church in Spanish lands, Arabian chieftain Mohammed ibn Saud, in 1744, allied himself with Muhammad ibn Abd al-Wahhab, leader of the Wahhab sect. The Wahhabis backed the Saud families in their methodical conquest of the entire Arabian peninsula, and, in turn, were allowed to control Saudi social society as the dominant and only fully recognized religion. Believing in the basics of Islam, they enforced a strict interpretation of the Koran.