Formation of Saudi Arabia

The unification of Saudi Arabia also known as the formation of Saudi Arabia was a series of military and political campaigns in which the various tribes, sheikhdoms, city-states, emirates, and kingdoms of most of the Arabian Peninsula were brought under the rule of the House of Saud. Unification began in 1902 and culminated in 1932, when the Kingdom of Saudi Arabia was proclaimed under the leadership of Ibn Saud, marking the establishment of what is known as the Third Saudi state, the successor to the First Saudi state and the Second Saudi state. A brief final phase of consolidation continued into 1934.

The House of Saud had been in exile in the British-protected Emirate of Kuwait since 1893, following their second removal from power and the dissolution of their polity by the Rashidi dynasty rulers of the Emirate of Jabal Shammar, allies of the Ottoman Empire.

In 1902, Ibn Saud returned to Najd and recaptured Riyadh, the former capital of the House of Saud. He subsequently consolidated control over much of the Arabian Peninsula, subjugating the remainder of Najd, seizing Al-Hasa from the Ottoman Empire, and conquering the Emirate of Jabal Shammar and the Hejaz from the Kingdom of Hejaz home to the Muslim holy cities of Mecca and Medina between 1913 and 1925.

The resulting state was known as the Kingdom of Hejaz and Najd from 1926 until it was renamed the Kingdom of Saudi Arabia in 1932. Two years later, in 1934, following the formal conclusion of the unification, the Kingdom of Yemen launched a war against Saudi Arabia. Saudi forces emerged victorious, ending Yemeni claims to the southern provinces of Asir, Najran, and Jazan. The Saudi–Yemeni War is often considered part of the broader unification process and is sometimes described as its second phase.

It has often been claimed that this process caused some 400,000 to 800,000 casualties. However, recent research suggests that though bloody, the number of deaths and injuries was significantly lower.