One consequence of the British failure to predict or contain the serious anti-Jewish riots and massacres of 1929 was the beginnings of a debate within some sections of the Yishuv (the Jewish population of Palestine) as to whether or not a policy of restrained defence was truly sufficient to safeguard Jewish life and property. It was felt by some that the Hagana (‘Defence’), a Jewish militia formed in the wake of the 1920 riots, had not been able to adequately protect Jewish settlers and land. (Officially illegal, the Hagana was in effect tacitly sanctioned by the Mandate authorities, and would occasionally be aided by them.) In the months following the 1929 riots, senior commanders of the Jerusalem Hagana split away, forming a splinter group with a more radically nationalist and proactively military ideology. During the Arab revolt of 1936-39, when the issue of  ‘restraint or retaliation’ once more came to the fore, this initially small and ineffectual dissident group would decisively break with the Hagana and come to prominence as the Irgun Zvai Leumi, the ‘National Military Organisation’ (IZL) (Krämer 2008: 291; Zadka 1995: 15-16; the precise date of the Irgun’s formation seems to be in some dispute).

The IZL was not founded with anti-British actions in mind; rather, it was intended as an anti-Arab retaliation and attack force, and its first operations were accordingly directed against Arabs: shootings, bombs in public places, attacks on buses and similar. In the run-up to war there were however occasional actions directed against the British, and the publication of the notorious White Paper of May 1939, with its stated aim of definitively limiting immigration and its indication that Palestinian Arabs would eventually have jurisdiction over Jewish immigrant numbers, caused great consternation; but after the outbreak of hostilities in September 1939 there was overall consensus in the Yishuv that co-operation with the Allies was the major imperative. The years 1940-44 thus saw the IZL at peace with the British, though this decision was not without dissenters: in June 1940 an IZL commander, Abraham Stern, broke away from the organization to found the Lehi (Lohamei Herut Yisrael – the Fighters for the Freedom of Israel, also known as the ‘Stern gang’). An even more radical group than the IZL, the Lehi continued to act against British infrastructure and personnel even during the war and many, including Stern himself, were killed or arrested (Krämer op. cit.: 303).

However, by late 1943 the IZL (which from December that year would be under the leadership of Menachem Begin) were beginning to organise in earnest again, and the threat that the British might severely restrict or even halt Jewish immigration from Europe at such a critical moment stimulated a return to armed insurrection against the Mandatory power. Working with the more extreme Lehi, the IZL began a campaign of anti-British violence in early 1944, culminating in several attempts by the Lehi on the life of High Commissioner MacMichael, and the November 1944 assassination, again by the Lehi, of Lord Moyne, minister of state for the Middle East. The British response, in addition to the usual pattern of reprisals, was an appeal to the Jewish Agency, and through them to the Hagana, for assistance in suppressing the two militant groups; after the killing of Moyne, the Jewish Agency assented, fearing that a severe British military crackdown would be harmful to the long-term interests of the Yishuv. Thus began the Saison (the ‘hunting season’), around six months during which the Hagana actively helped the Mandate security services to track down and detain hundreds of IZL and Lehi cadres (Cohen ed. 1987: i-ii; Zadka op. cit.: 52-5).

This period drew to a close after the end of the War. The failure of the Jewish Agency to have gained any concessions from the British for their collaboration, and the apparent intention of Atlee’s newly elected Labour government to uphold the recommendations of the despised 1939 White Paper led to a radical reversal of the situation. Having withdrawn co-operation from the British, the Jewish Agency and the Hagana set out in the autumn of 1945 on a joint anti-British insurgency in collaboration with IZL and Lehi forces. (Intercepted telegrams between prominent Jewish Agency figures that indicate the depth and nature of the collaborative campaign were published in July 1946 in a British Command paper entitled Palestine: Statement of Information Relating to Acts of Violence [Cmd. 6873], see especially pages 4-9; this document is reproduced in facsimile in Cohen ed. op. cit.: 155-65.)

Despite the uneasy marriage between the three forces, this ‘Jewish Resistance Movement’, as it was termed in British official correspondence (e.g. Palestine: Statement…op. cit.: 3),  undertook a serious and sustained campaign of sophisticated and damaging strikes against British interests from late 1945 to mid-1946. The first major co-operative action, on the night of 31 October 1945, saw Palmach units (the elite strike force of the Hagana) cause explosions on the Palestinian railways system in no fewer than 153 places, and destroy three police launches in Haifa and Jaffa; the IZL simultaneously attacked Lydda station, damaging trains and equipment, while the Lehi made a failed attempt to blow up the Haifa oil refinery (ibid.). Further major operations included Palmach assaults on RAF radar stations, Police Mobile Force camps, airfields, bridges, and roads, and the kidnapping of British forces personnel (ibid.: 7; Zadka op. cit.: 68-71).

On the 22 July 1946, six IZL cadres dressed as Arab workmen planted bombs disguised as milk-cans in the basement of the King David Hotel, beneath the part of the building which housed the headquarters of the British government secretariat and army command. Ninety-one people were killed in the resulting explosion, and many more were injured. The bombing profoundly shocked opinion in both Britain and Palestine. Even though the Hagana had been aware of the plan for the attack, they subsequently dissociated themselves from the other two factions. The united resistance was abandoned, and the Hagana refrained from further coordinated attacks on the British, leaving the IZL and Lehi to continue their campaign alone.