Seeking to win over beduin tribal leaders and obtain their loyalty to him and his cause, Abd al Aziz established Ikhwan communities in which the beduin tribesmen could settle and adopt a sedentary way of life. The Ikhwan were supported by Abd al Aziz with land, seed, tools, and money, as well as arms and ammunition. A mosque was built in each community, and these mosques also served as military garrisons. By 1915 there were more than 200 settlements and in excess of 60,000 men in readiness to heed Abd al Aziz's call for warriors in his continuing battles to unite the peninsula.

The Ikhwan became dedicated, even fanatical followers of the young Al Saud leader. Acquiescence to discipline was not an Ikhwan virtue, but Abd al Aziz was an uncommon leader able to use the power of the brotherhood and its prowess in battle to his advantage. The greatest of the Ikhwan successes was the conquest of the Hijaz after World War I, but the bold exploits of the Ikhwan also marked the beginning of their end. When Sharif Hussein, the Hashimite ruler of the Hijaz, entered into military negotiations with the Al Rashid, Abd al Aziz's reaction was swift and harsh. He sent the Ikhwan against the Al Rashid stronghold at Hail, which was captured with little difficulty in 1921. Emboldened by their success, the warriors disregarded orders and crossed the border into Transjordan. The raiding and plundering of their Hashimite ally aroused the British, who counterattacked with devastating effect, using armored cars and aircraft.

Other Ikhwan expeditions succeeded in overpowering Asir, an independent enclave in the southwest. In defiance of Abd al Aziz's authority, however, they continued to raid the British protectorates. Recognizing that the wild forays of the Ikhwan could only be a constant irritant and source of danger to his leadership, Abd al Aziz began to form a more conventional and more disciplined army. He entered Mecca and laid siege to Jiddah and Medina, which were occupied by the end of 1924. These successes led to the capitulation of the Hashimite kingdom of the Hijaz, leaving the Al Saud in control of the entire peninsula, except for Yemen in the southwest and the British gulf protectorates.

Having acquired such a tremendous area, Abd al Aziz then faced the daunting task of governing it. First, however, he had to deal with the rebellious Ikhwan. The zealots of the brotherhood regarded the Western-influenced modernization pursued by Abd al Aziz as a betrayal of the fundamentals of Islam that had been their raison d'être since the beginning of their association with the House of Saud. Renewed Ikhwan raids against defenseless groups in Iraq incensed the British, who were trying to stabilize the region, and finally compelled Abd al Aziz to force the submission of the Ikhwan. When the Ikhwan leadership revolted against Abd al Aziz, he took to the field to lead his army, which was now supported by four British aircraft (flown by British pilots) and a fleet of 200 military vehicles that symbolized the modernization that the Ikhwan abhorred. After being crushed at the Battle of Sabalah,859 h, the Ikhwan were eliminated as an organized military force in early 1930.

The suppression of the Ikhwan brought to an end the chronic warfare in the Arabian Peninsula except for a series of incidents between 1931 and 1934 along the poorly defined border with Yemen. Abd al Aziz placed his eldest son, Saud, at the head of an army that succeeded in occupying much Yemeni territory but could not defeat the Yemeni warriors so adept at defending their mountain passes. Pressure by European powers determined to maintain the status quo on the Arabian Peninsula finally brought peace, and much of the occupied territory was restored to Yemen.

During the 1930s, Abd al Aziz, who had made himself king, allowed the remnants of the Ikhwan to regroup as a beduin militia. They became known as the White Army because they wore traditional white robes rather than military uniforms. For Abd al Aziz, the White Army served as a counterbalance to the small regular army, thereby helping to ensure his control over internal security. In addition to the two armies, there was the Royal Guard, a lightly armed body of absolutely loyal officers and troops, whose mission consisted entirely of protecting the monarch and the growing royal family.

Data as of December 1992