Irgun Bet was established in 1931 by Jerusalem Hagana dissenters, and was joined by dissenters in other places. After Irgun Bet had reunited with Hagana in 1937, some of its members parted and established Etzel (Irgun Z'vai Leumi). Some of Etzel members who opposed collaboration between Etzel and the British, established Lechi. Etzel and Hagana collaborated with the British throughout World War II.
In 1944 Etzel declared a revolt against the British, and initiated violent attacks, mainly on British installations, while Lechi attacked British military officers and policemen. From 1944 onwards both organizations intensified their operations, including blackmail and robbing of Jewish individuals and facilities defended by the Hagana, in order to support their operations.
The Jewish national institutions were afraid that the operations of the defector organizations would severe British policy and sanctions against the Yishuv, demanded cessation of their unauthorized separate operations. Lechi acceded, while Etzel refused and carried on its activities. Therefore, the Hagana gave Etzel's leader, Menahem Begin, an ultimatum to cease their separate attacks against the British. Preventive measures were taken against Etzel since it refused to comply. The operations against Etzel were called the "Saizon" (season). Etzel members were detained and kept in Hagana custody, while others were handed over to the British. Both sides suffered a small number of casualties during these clashes. In order to avoid bloodshed and a war between brothers, Begin ordered his men to temporarily abstain from resistance. After a pause, in 1947, Hagana resumed its firm actions against Etzel since it had refused to cease its activities. This time Etzel responded violently but bloodshed was avoided.
During the first months of Israel's War of Independence, Lechi and Etzel operated mainly in the major cities, while collaborating with Hagana to a certain extent. With the establishment of the Israeli army (IDF), Lechi was dismantled and was incorporated in two IDF battalions. Etzel too joined the IDF but after the Altalena ship incident. Its units were dismantled and their members dispersed among several IDF brigades. In September 1948, after the murder of Count Bernadot, the rest of the dissident groups who still operated in Jerusalem, were finally dismantled and their members were formally enlisted into the IDF.