The Department of Defense, officially the Department of Defense for the Republic of Ireland is an ministerial department of the Irish government tasked with governing the defense and military of the country. The Department of Defense is the largest governmental employer with over 360,000 registered on its payroll. This includes the Local Defence Force and the Irish Armed Forces and its civil servants.

The head of the department of defense is the Minister for Defence who oversees operations of the department along with the Secretary for Defence. Within the department of defense is 4 sub departments; Department of the Army, Department of the Air Force, Department of the Navy and the Department of Coastal Defense.

The Department of Defense also operations various agencies such as; the Military Intelligence Agency, Domestic Security Bureau and the National Defence Academy.


From 1905-1919 the departments of the navy, air force and army were all managed separately and all had to communicate like all other separate this caused bad communications due to the departments were always in contact. World War I was a disaster for the departments until the Wartime Communications Center was set up for direct communications between commanders. In 1919 Jordan Curtis was appointed as Minister for Security. This was during the 1920 Irish Recession and he was appointed all ministerial positions of the armed forces departments. Due to the hectic communications he began the Defence Act 1920. This reformed the entire armed forces departments and merged all departments into one. The act was brought into the Oirechtas in 1920 and was widely accepted.