IDF stands for Israel Defense Forces, which is the national military of the State of Israel. It includes ground forces, air force, and navy, and its mission is to defend the existence, territorial integrity, and sovereignty of the state of Israel, protect its inhabitants, and combat all forms of terrorism that threaten daily life. Israeli law requires that all Israeli citizens and permanent residents begin serving in the Israeli army at the age of 18, with men required to serve three years and women to serve 20-21 months. All non-Jewish women, Arab men (except Druze), and Haredi Jews were automatically exempt from service, although volunteers from these groups are occasionally admitted, and the Israeli state encourages some Bedouins to join. Reserve service is required until the age of 51 in the case of men and 24 in the case of women.