Najd
16th century to the unification of Saudi Arabia

In the 16th century, the Ottomans added the Red Sea and Persian Gulf coast (the Hejaz, Asir and al-Ahsa) to the Empire and claimed suzerainty over the interior. One reason was to thwart Portuguese attempts to attack the Red Sea (hence the Hejaz) and the Indian Ocean.

Ottoman control over these lands varied over the next four centuries with the fluctuating strength or weakness of the Empire's central authority. The emergence of what was to become the Saudi royal family, known as the Al Saud, began in Najd in central Arabia in 1744, when Muhammad bin Saud, founder of the dynasty, joined forces with the religious leader Muhammad ibn Abd al-Wahhab, founder of the Wahhabi movement, a strict puritanical form of Sunni Islam.

This alliance formed in the 18th century provided the ideological impetus to Saudi expansion and remains the basis of Saudi Arabian dynastic rule today. The first "Saudi state" established in 1744 in the area around Riyadh rapidly expanded and briefly controlled most of the present-day territory of Saudi Arabia, but was destroyed by 1818 by the Ottoman viceroy of Egypt, Mohammed Ali Pasha.

A much smaller second "Saudi state", located mainly in Nejd, was established in 1824 by Turki bn Abdullah. Throughout the rest of the 19th century, the Al Saud contested control of the interior of what was to become Saudi Arabia with another Arabian ruling family, the Al Rashid. By 1891, the Al Rashid were victorious and the Al Saud were driven into exile in Kuwait.

At the beginning of the 20th century, the Ottoman Empire continued to control or have suzerainty over most of the peninsula. Subject to this suzerainty, Arabia was ruled by a patchwork of tribal rulers, with the Sharif of Mecca having pre-eminence and ruling the Hejaz.

In 1902, Abdul Rahman 's son, AbdulAziz—later to be known to the west as Ibn Saud —recaptured control of Riyadh, bringing the Al Saud back to Najd. Ibn Saud gained the support of the Ikhwan, a tribal army inspired by Wahhabism, and which had grown quickly after its foundation in 1912. With the aid of the Ikhwan, Ibn Saud captured al-Ahsa from the Ottomans in 1913.

In 1916, with the encouragement and support of Britain (which was fighting the Ottomans in World War I), the Sharif of Mecca, Hussein bin Ali, led a pan-Arab revolt against the Ottoman Empire to create a united Arab state. Although this revolt failed in its objective, the Allied victory in World War I resulted in the end of Ottoman suzerainty and control in Arabia.

Ibn Saud avoided involvement in the Arab Revolt and instead continued his struggle with the Al Rashid. Following the latter's final defeat, he took the title Sultan of Najd in 1921. With the help of the Ikhwan, the Hejaz was conquered in 1924–25 and on 10 January 1926, Ibn Saud declared himself King of the Hejaz. A year later, he added the title of King of Nejd. For the next five years, he administered the two parts of his dual kingdom as separate units.

After the conquest of the Hejaz, the Ikhwan leadership turned to expansion of the Wahhabist realm into the British protectorates of Transjordan, Iraq and Kuwait, and began raiding those territories. This met with Ibn Saud's opposition, as he recognized the danger of a direct conflict with the British. At the same time, the Ikhwan became disenchanted with Ibn Saud's domestic policies, which appeared to favor modernization and the increase in the number of non-Muslim foreigners in the country. As a result, they turned against Ibn Saud and, after a two-year struggle, were defeated in 1930 at the Battle of Sabilla, where their leaders were massacred. In 1932 the two kingdoms of the Hejaz and Nejd were united as the Kingdom of Saudi Arabia.
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