Nomadic tribes have inhabited the Arabian Peninsula long before Islam. The Islamic prophet Muhammad unified these tribes to form a single Islamic religious kingdom. Following his death in 632, Muslim dominion quickly spread over the Middle East, from Spain to portions of the Indian subcontinent.
The Ottoman Empire originally took control of the region in the 16th century, and while numerous sultanates arose from time to time, it wasn't until the Ottoman Empire collapsed at the end of World War I that modern Saudi Arabia appeared.
Ibn Saud (the son of Abdul Rahman bin Faisal, the final monarch of the 'Second Saudi State') became Sultan of Najd, Arabia's centre area, in 1921.
After capturing the Hejaz (western Arabia) in 1925, Ibn Saud was named King of the Hejaz on January 10, 1926. In 1927, he altered his title to King of Nejd.
Despite being the King of both areas, he ruled them individually for the next five years. The kingdoms of the Hejaz and Nejd were renamed and united as the Kingdom of Saudi Arabia only in 1932, following a two-year war to subdue and destroy erstwhile allies.
Saudi Arabia's National Day became a public holiday in 2007. In 2005, Saudi Arabia's late King Abdullah bin Abdulaziz declared that the 75th National Day will become an annual national holiday.
