Historians have misunderstood the causes of the 1939 White Paper, which abandoned Britain’s long-held Zionist policy. They tend to attribute cause to the Arab rebellion in Palestine. In fact, Britain’s decision to limit Jewish immigration to Palestine was taken despite the rebellion and its leader, the ex-Mufti of Jerusalem, Amin al-Husseini. Recently declassified signals intelligence intercepts, as well as recently released records in Israeli archives, reveal that the main consideration for this dramatic change was Britain’s desire to foster good relations with the founding King of Saudi Arabia, ‘Abdul ‘Aziz ibn Sa’ud. Palestinian leaders and the pan-Arab movement looked to ibn Saud’s figurehead leadership. They saw the king as the ‘Bismarck of Arabia’, who would eventually unite the Arabic speaking peoples. Palestinian leaders often tried to exploit his influence. In particular, the Mufti took pride in his role in successful Saudi-Yemen peace talks, and enjoyed popular attention during the visit to Palestine of the King’s son. Between 1932 and 1935, the pan-Arab movement, including the Mufti, discussed different ways of leveraging a European war or crisis for the sake of the independence of Mandated Arab territories. In late 1935, at a time of palpable pan-Arab unity, the Italian-Abyssinian crisis made the possibility seem very real. This led to a successful general strike and concessions in Syria. Britain’s reaction to the Palestine rebellion was more forceful. Throughout the rebellion, King ‘Abdul ‘Aziz maintained a partnership of shared interest with Britain. The ‘Bismarck of Arabia’ mastered realpolitik. He caused the Mufti to call off the general strike and rebellion in October 1936. He remained suspicious of the Mufti’s motives and intentions, and those of other powers such as Italy. The King reported such issues to British diplomats, who confirmed his honesty and openness by reading his cable and wireless traffic. Signals intelligence confirmed that Ibn Saud was hostile to Britain’s enemies, but maintained considerable figurehead status in the pan-Islamic and pan-Arab worlds. After an expensive and bloody counter-rebellion in Palestine, whose climax coincided with the Munich crisis, Britain realized the need to impose a solution on the Palestine problem. In a future world war, Britain needed a reliable base of support outside its own mandated territories, protectorates, and semi-independent client states. By granting concessions in the White Paper to ibn Sa’ud, British policy sought to boost his prestige over the movement, and to leverage it.