The Irgun, officially known as the National Military Organization in the Land of Israel, was a Zionist paramilitary organization that operated in Mandatory Palestine from 1931 to 1948. Founded as an offshoot of the larger Jewish paramilitary group Haganah, the Irgun emerged in response to perceived inadequacies in Haganah's defensive posture against Arab attacks during the 1929 riots. Led by figures like Vladimir Jabotinsky and later Menachem Begin, the Irgun advocated a more aggressive Revisionist Zionist ideology, aiming to establish a Jewish state on both sides of the Jordan River through militant actions. It conducted sabotage, assassinations, and bombings against British Mandate authorities and Arab targets, positioning itself as a nationalist resistance force during the period of British rule. The Irgun's activities escalated during the 1930s and 1940s, including high-profile operations such as the 1946 bombing of the King David Hotel in Jerusalem, which killed 91 people and was condemned internationally as a terrorist act. It was also implicated in the 1948 Deir Yassin massacre, where over 100 Palestinian villagers were killed, an event widely criticized as a war crime. The group clashed with both British forces and rival Jewish organizations like Haganah and Lehi, leading to internal Jewish conflicts. British authorities labeled the Irgun a terrorist organization, offering rewards for its leaders' capture, and it faced allegations of smuggling arms and illegal immigration to bolster Jewish presence in Palestine. Following Israel's Declaration of Independence on 1948-05-14, the Irgun merged with the Israeli Defense Forces (IDF) in 1948, effectively disbanding as an independent entity. Many of its members integrated into the IDF, and leaders like Menachem Begin transitioned to politics, founding the Herut party which influenced Israel's Likud. The Irgun's legacy remains controversial: hailed by some as freedom fighters who contributed to Israel's founding, but condemned by others for tactics involving civilian casualties and extremism. It operated without formal headquarters due to its clandestine nature, but was primarily based in urban centers like Tel Aviv and Jerusalem in Mandatory Palestine.