World War II erupted shortly after the issuance of the White Paper. However, it soon became evident that the British and the Jews of Palestine shared a common enemy. Four days before the German invasion of Poland, Chaim Weizmann, leader of the World Zionist Organization, wrote to British Prime Minister Chamberlain stating,

The Jewish Agency has recently had differences in the political field with the Mandatory Power. We would like these differences to give way to the greater and more pressing necessities of the time.

Once the war commenced, the Yishuv mobilized all of its resources to aid the British war effort. The amount of cultivated land, for increased production of food, expanded by 70%. All factories in Palestine began manufacturing war-related items. Everything from tank treads to uniforms was produced in the factories of Jewish Palestine. During the war, the number of factories tripled, and by 1945, 63% of the working population of Jewish Palestine was engaged in producing war products.

At the outset of WWII, the Va’ad Leumi (National Committee) announced it would register people for national service. 136,000 signed up in the first five days. The Jewish Agency sought to organize Jewish soldiers into a special unit, similar to what happened during World War I. British officials in the Middle East opposed the idea, and temporarily blocked the initiative.

However, when Winston Churchill replaced Chamberlain as Prime Minister in 1940, British policy began to change. Churchill was open to the idea and wrote to Colonial Secretary Lord Lloyd, asserting,

The cruel penalties imposed by your predecessor upon the Jews of Palestine for arming have made it necessary to tie up needless forces for their protection. Pray let me know exactly what weapons the Jews have for self-defense.

Churchill met with Weizmann for lunch on September 6, 1940, and assured Weizmann of his support for the project to start a Jewish army. After the meeting, Churchill sent a memorandum ordering the recruitment of as many Palestinian Jews as possible to form Jewish battalions. Since the Colonial Office insisted there be an equal number of Jews and Arabs in the units, and more Jews than Arabs were expected to volunteer, the surplus Jewish volunteers were to be sent to Egypt for regular military training. Lord Lloyd died suddenly and was replaced by Lord Moyne, who, along with British officials in the Middle East, succeeded in delaying the plan. Despite this, Jews volunteered, and by August 1942, there were 18,000 Jews in Jewish battalions as part of the British Army. In total, it is estimated that 30,000 Jews became part of Jewish forces serving in nearly all branches of the British army during the war.

During the darkest days of the war, when it appeared that German forces commanded by General Rommel might break through Egypt, the Haganah developed what was called “the Carmel Plan”. This was a strategy to defend a region in the Carmel Mountains that would become a refuge for all Jews of Palestine. Additionally, during this time, the British sought help from the Haganah and its Palmach branch to prepare for the British invasion of Syria. The Palmach carried out reconnaissance operations, one of the mission’s leaders being Moshe Dayan, who lost an eye during an encounter with enemy forces.

The experience of so many Jews from Palestine in the British army proved invaluable for defending Israel in the War of Independence.