 Complete the following phrase:  During the First World War, an Arab Revolt, supported by Britain, succeeded in removing the Ottomans from the Arabian peninsula; in the period following this Ibn Saud managed to expand his kingdom considerably, eventually proclaiming the Kingdom of Saudi Arabia in 1932. In the south-west the Idrisid Emirate of Asir had taken advantage of the Ottoman withdrawal and declared independence in 1917, only to be annexed by the Saudis in 192630. More successful was the Mutawakkilite Kingdom of Yemen later known as the Yemen Arab Republic or North Yemen further south, which declared independence in 1918. North Yemen and Saudi Arabia had no defined frontier and disputed ownership of border territories notably Asir, Jizan and Najran, claimed by North Yemen as part of Greater Yemen; these tensions culminated in a 