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.