Irgun, was a
Jewish underground movement founded in 1931 by ex-
Haganah leaders. This group split in 1937, half returning to the Haganah, the other half forming a new
Zionist Irgun. It's full name is spelt "Irgun Zeva'i Le'umi" or "Irgun Zvai Leumi" (IZL) and also known as "Etzel" or "The National Military Organisation".
It was led by Ze'ev Jabotinsky, and was linked to the Revisionist Movement. Irgun was effectively a violent organisation. Preferring a more active approach to politics. Their approach was not appreciated by British authorities, and many were arrested. Shlomo Ben Yosef was hanged after he shot at an Arab bus.
Irgun turned its attention to the British Mandate authorities, after the publication of the famous White Paper in 1939. However, the outbreak of war changed things quite considerably. A truce was declared, and Irgun joined the good fight.
Menachem Begin, began his leadership of Irgun in 1943, where he promptly declared war against Britain in February 1944 (well, British Administration to be exact). "War" however was little but glorified terrorism (depending on how you define it), attacking government offices, police stations etc. The Jewish Agency and the Haganah, joined up to fight against Irgun in a campaign called Sezon.
The peak of Irgun's attacks came in 1946, the King David Hotel bombing (July 22nd), where Irgun killed 91 people (17 of whom were Jews). Later that year they bombed the British Embasy in Rome (October 31).
4 Irgun members were hanged in April 1947. The following month, Irgun stormed the prison and freed 41 prisoners. The British responded in July by executing 3 more members, Irgun retaliated by hanging two British Sergeants.
Irgun then bombed a police station in Haifa, Palestine, four British, and four Arab policemen were killed, along with two Arab civilians (September 29 1947). Later that year they attacked a cafe in Jerusalem with grenades. 11 Arabs and 2 British policemen were killed.
In April '48 - Irgun fought with Palestinian soldiers in what was named the Deir Yassin incident during the battle for Israel's independence. The Irgun is alleged to have killed 254 Arab women and children during this battle. This is disputed.
After the Declaration of Independence, Irgun began to integrate into the IDF, although there was still an Irgun command. When Irgun attempted to smuggle weapons in Israel on the ship, Altalena, it was sunk by the IDF. This was the last action of Irgun, and it completed its merge.
Sources:
www.onwar.com
The Pedagogic Center, The Department for Jewish Zionist Education, The Jewish Agency for Israel
www.us-israel.org
http://www.cdiss.org/