That area was under nominal suzerainty by the Ottoman Empire off and on from the early 16th century until 1914. The inhabitants mostly governed themselves during these periods, which included the lead-up to WWI. The start of WWI was shortly after the second Saudi state had ended in 1891, having been ruled by Rahman bin Faisal Al Saud, who was mostly concerned with 2 things: fighting off rivals, and granting Muslim pilgrims access to Mecca and Medina.

If you are interested in the history of the House of Saud, a good entry level book written from both male and female perspective is A Journey Through Islamic History: A Timeline of Key Events by Yasminah Hashim and Muhammad Abdul Jabbar Beg.

The region in the central Arabic peninsula down to Yemen is arid desert, and the majority of this region was occupied by Arabic Bedouins, who never had any political power to speak of, but are really a fascinating group. They are nomadic, and would often follow their herds, living off the milk and meat from goats and sheep and camels, and trading mostly wool for food and other goods which they could not produce themselves.

The most extreme example of the Arabic bedouins would be a lone Bedouin man who owns a single female camel as his only notable possession (other than minimal clothing, a blanket, a knife, and a few other small essential or cultural items). The camel knows how to survive in the desert, so the man would keep a lead rope around its neck as much as possible and follow the camel through the desert wherever it went, surviving 95% off the camel’s milk. Some of these Bedouin men were known to spend years or even a decade wandering the desert without seeing any other people, until their camel one day leads them back into a settlement, or other inhabited area.

If you are interested in learning more about the history and society of the Bedouins, I highly recommend the book The Bedouins and the Desert: Aspects of Nomadic Life in the Arab East (SUNY series in Near Eastern Studies) by Jibrail S. Jabbur.