After the Irgun proclamation of February 1944 the Agency attempted to negotiate with both the Irgun and Lehi to bring a halt to their violence but without success. Both Lehi and Irgun refused to recognize the authority of an Agency, on the grounds that none of their officers had been democratically elected. When, on November 6, 1944 Lehi members Eliyahu Hakim and Eliyahu Bet-Zuri assassinated the British Resident Minister of state, Lord Moyne, David Ben Gurion decided the only solution to violence in Palestine the was to co-operate with the British in bringing down the Irgun and Lehi.

The Agency appointed, as leader of a special Unit, Shimon Avidan, an experienced fighter who had seen action in the Spanish Civil War and had led the "German Unit" of the Palmach, responsible for conducting guerrilla operations against the Axis.

(The photo on the left shows Shimon Avidan.)

The special Unit was composed of Palmach and Shai members dedicated to hunting out Irgun members. The period between 1944 and 1945 when Haganah members hunted down Irgun came to be known as Le Saison. Unit squadrons arrested Irgun members in many kibbutzim and imprisoned them in a Watch-Tower in Kiryat Anavim. They handed the Irgun vice-commander, Ya'acov Meridor, over to the police, but kept Ya'acov Tavin, head of the Irgun intelligence, in solitary confinement at Ein Harod for six months. In addition to the kidnappings, dozens of Irgun members and supporters were fired from their jobs and students were expelled.

The unit discovered a list of Irgun donors which they gave to Teddy Kollek, the Agency-appointed contact with MI5 and British military intelligence. Kollek handed the list to MI5 who passed it on to the CID. Thanks to this information, the police were able to arrest several Irgun leaders and hundreds of its members. Some Irgun members were deported to detainment camps in Africa (mostly in Eritrea). The Irgun leader,Menachem Begin, was not found but it was probably only his command to his men not to react violently to Haganah arrests that prevented internecine war between Jews similar to that being waged between Arab political parties( (The photo shows Menachim Begin in the uniform of the Free Polish Army. He entered Palestine as member of the Polish Army )