In December 1947 , immediately following the UN partition vote , the 1947-48 Civil War in Mandatory Palestine broke out between the Yishuv and Palestinian Arabs . The Irgun fought together with the Haganah and Lehi during that period . Notable operations in which they took part were the battles of Jaffa and the Jordanian siege on the Jewish Quarter in the Old City of Jerusalem . The Irgun 's most controversial operation during this period , carried out alongside Lehi , was an assault on the Arab village of Deir Yassin in which more than a hundred villagers and four of the attackers were killed . The event later became known as the Deir Yassin massacre , though Irgun and Lehi sources would deny a massacre took place there . Begin also repeatedly threatened to declare independence if the Jewish Agency did not do so
Deir Yassin massacre
Deir Yassin massacre
Menachem Begin