The reign of Abdulaziz bin Muhammad began in 1765 when his father died. Although his father was titled as Emir, Abdulaziz was given the titles of both Emir and Imam. However, the latter title was not granted immediately after his succession to the throne, but it was given later. Imam as a title was a reflection of Abdulaziz's religious education by Muhammad bin Abdul Wahhab and his deeply religious personality. His younger brother,
Abdullah, unsuccessfully challenged the rule of Abdulaziz.{{cite journal|author1=Abdullah Hazaa Othman|author2=Oleg Evgenievich Grishin|volume=13|author3=Bakil Hasan Nasser Ali|title=The Conflict Wings in the Saudi Political System|journal=Journal of Politics and Law|year=2020|issue=3|page=65|doi=10.5539/jpl.v13n3p64 Abdulaziz's father, Muhammad bin Saud, initiated attacks against the ruler of Riyadh, Dahham bin Dawwas, in 1747.{{cite journal The expansion continued with the capture of
Qatif in 1794{{cite thesis|author=Abdulaziz Mohamed Hasan Ali Al Khalifa|title=Relentless Warrior and Shrewd Tactician: Shaikh Abdullah bin Ahmad of Bahrain 1795-1849 A Case Study of Shaikhly Statecraft in the Nineteenth Century Gulf|degree=PhD|date=April 2013|page=73|url=https://ore.exeter.ac.uk/repository/handle/10871/12461?show=full|hdl=10871/12461 In 1802
Hejaz, namely
Taif and Khurma, was captured,{{cite thesis|author=Nawaf bin Ayyaf Almogren|title=Diriyah Narrated by Its Built Environment: The Story of the First Saudi State (1744-1818)|url=https://dspace.mit.edu/handle/1721.1/127856|hdl=1721.1/127856 In 1802 Bahrain was invaded and captured by the ruler of
Muscat. Abdulaziz bin Muhammad recaptured it in addition to Qatar and appointed there a governor, Abdullah bin Ufaysan, there. The rulers of Bahrain,
Abdullah and Salman, together with their families were sent to Diriyah where they were all detained.{{cite thesis|author=Abdul Wahap Saleh Babeair|title=Ottoman Penetration of the Eastern Region of the Arabian Peninsula, 1814-1841|url=https://www.proquest.com/docview/303386071 ==Sack of Karbala==