Yemeni–Adenese clan violence refers to sectarian violence in Yemen and Aden during 1956-60, resulting in some 1,000 deaths. In 1950, Kennedy Trevaskis, the Advisor for the Western Protectorate drew up a plan for the British 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, the leader of the Mutawakkilite Kingdom of Yemen. 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.