news of Arab nationalism from the outside world on newly available transistor radios. Challenges to the status quo British control was also challenged by King Ahmad bin Yahya of the Mutawakkilite Kingdom of Yemen to the north who did not recognise British suzerainty in South Arabia and had ambitions of creating a unified Greater Yemen. In the late 1940s and the early 1950s, Yemen was involved in a series of border skirmishes along the disputed Violet Line, a 1914 Anglo-Ottoman demarcation that served to separate Yemen from the Aden Protectorate. In 1950, Kennedy Trevaskis, the Advisor for the Western Protectorate drew up a plan for the protectorate states to form two federations, corresponding to the two-halves of the protectorate. Although little progress was made in bringing the plan to fruition, it was considered a provocation by Ahmad bin Yahya. In addition to his role as king, he also served as the imam of the ruling Zaidi branch of Shi'a Islam. He feared that a successful federation in the Shafi'i Sunnite protectorates would serve as a beacon for discontented Shafi'ites who inhabited the coastal regions of Yemen. To counter the threat, Ahmad stepped up Yemeni efforts to undermine British control and, in the mid-1950s, Yemen supported a number of revolts by disgruntled tribes against protectorate states. The appeal of Yemen was limited initially in the protectorate but a growing intimacy between Yemen and the popular Arab nationalist president of Egypt Gamal Abdel Nasser and the formation of United Arab States increased its attraction. Federation and the end of the Protectorate Aden had been of interest to Britain as a link to British India and then, after the loss of most of Britain's colonies from 1945 and the disastrous Suez Crisis in 1956, as a valuable port for accessing crucial Middle Eastern oil. It had also been chosen as the new location for Middle East Command. Nationalist pressure prodded the threatened rulers of the Aden Protectorate states to revive efforts at forming a federation and, on 11 February 1959, six of them signed an accord forming the Federation of Arab Emirates of the South. In the next three years, they were joined by nine others and, on 18 January 1963, Aden Colony was merged with the federation creating the new Federation of South Arabia. At the same time, the (mostly eastern) states that had not joined the federation became the Protectorate of