By 1906, Abdulaziz had driven the Al Rashid out of Najd and the Ottomans recognized him as their client in Najd. His next major acquisition was Al-Hasa, which he took from the Ottomans in 1913, bringing him control of the Persian Gulf coast and what would become Saudi Arabia's vast oil reserves. He avoided involvement in the Arab Revolt, having acknowledged Ottoman suzerainty in 1914, and instead continued his struggle with the Al Rashid in northern Arabia. In 1920, the Ikhwan's attention turned to the south-west, when they seized Asir, the region between the Hejaz and Yemen. In the following year, Abdul-Aziz finally defeated the Al Rashid and annexed all northern Arabia.