The new army organized itself when the 1947–48 Civil War in Mandatory Palestine escalated into the 1948 Arab–Israeli War, which saw neighbouring Arab states attack.
Twelve infantry and armored brigades formed: Golani, Carmeli, Alexandroni, Kiryati, Givati, Etzioni, the 7th, and 8th armored brigades, Oded, Harel, Yiftach, and Negev.
The number of wars and border conflicts in which the IDF has been involved in its short history makes it one of the most battle-trained armed forces in the world.
While originally the IDF operated on three fronts—against Lebanon and Syria in the north, Jordan and Iraq in the east, and Egypt in the south—after the 1979 Egyptian–Israeli Peace Treaty, it has concentrated its activities in southern Lebanon and the Palestinian Territories, including the First and the Second Intifada.
In 1965, the Israel Defense Forces was awarded the Israel Prize for its contribution to education.
The IDF uses several technologies developed in Israel, many of them made specifically to match the IDF's needs, such as the Merkava main battle tank, Achzarit armoured personnel carrier, high tech weapons systems, the Iron Dome missile defense system, Trophy active protection system for vehicles, and the Galil and Tavor assault rifles.
Bar-Giora was transformed into Hashomer in April 1909, which operated until the British Mandate of Palestine came into being in 1920.After the 1920 Palestine riots against Jews in April 1920, the Yishuv leadership realised the need for a nationwide underground defense organization, and the Haganah was founded in June of the same year.The Haganah became a full-scale defense force after the 1936–1939 Arab revolt in Palestine with an organized structure, consisting of three main units—the Field Corps, Guard Corps, and the Palmach.The Israel Defense Forces are believed to have had an operational nuclear weapons capability since 1967, possibly possessing between 80 and 400 nuclear weapons,).The name was chosen because it conveyed the idea that the army's role was defense, and because it incorporated the name Haganah, the pre-state defensive organization upon which the new army was based.Immediately after the 1948 war, the Israel-Palestinian conflict shifted to a low intensity conflict between the IDF and Palestinian fedayeen.