Unification of Saudi Arabia

The unification 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.

Source: Wikipedia — Unification of Saudi Arabia (CC BY-SA 4.0)