The title Defence Minister, Minister for Defense, Minister of National Defense, Secretary of Defense, Secretary of State for Defence or some similar variation, is assigned to the person in a cabinet position in charge of a Ministry of Defense, which regulates the armed forces in sovereign states. The role of a defence minister varies considerably from country to country; in some the minister is only in charge of general budget matters and procurement of equipment; while in others the minister is also, in addition, an integral part of the operational military chain of command.
Prior to the 20th century, there were in most countries separate ministerial posts for the land forces (often called "minister for war") and the naval forces. In the interwar period, some countries created a separate ministerial post in charge of the air forces. After the end of World War II, the trend in most countries was to merge the several separate ministerial posts into a single defence minister in charge of all the armed forces. Another common reform which occurred at the end of World War II was to place the defence minister in a national security council, war cabinet, or a "Kitchen Cabinet", which allows the head of government or head of state to coordinate military, diplomatic and economic activities.
The Defence Ministry in some countries is a very important ministry, sometimes considered more important than the foreign ministry. If war is common for a country, the defence minister's position is often assumed by the head of government. (For example, five Prime Ministers of Israel have held the Defense (Security) Ministry during their Premiership). In some nations there is a strong convention that the defence minister has to be a civilian, in order to highlight civilian control over the military, though it's not uncommon for the defence minister to have some (or even extensive) military experience.
The People's Republic of China is very unusual in that the Ministry of National Defence (MND) is relatively powerless; it does not have command over the People's Liberation Army. Command of the military belongs in the party and in the state Central Military Commission (CMC); the MND exists primarily as a liaison and protocol office to communicate with foreign militaries. Essentially, the MND exists only because most other nations have defence ministries, and for protocol and liaison purposes, the PRC needs to have an institution corresponding with those of other governments. However, the Minister of National Defence (who is usually a senior, although not always the highest ranking, military officer) is always a CMC member and usually a Vice Chairman and State Councillor, and this is an authoritative position.
The 1947 law also caused far-reaching changes in the military establishment. The War Department and Navy Department merged into a single Department of Defense under the Secretary of Defense, who also directed the newly created Department of the Air Force. However, each of the three branches maintained their own service secretaries. In 1949 the act was amended to give the Secretary of Defense more power over the individual services and their secretaries.
The Council itself included the President, Vice President, Secretary of State, Secretary of Defense, and other members (such as the Director of the Central Intelligence Agency), who met at the White House to discuss both long-term problems and more immediate national security crises. A small NSC staff was hired to coordinate foreign policy materials from other agencies for the President. Beginning in 1953 the President's Assistant for National Security Affairs directed this staff. Each President has accorded the NSC with different degrees of importance and has given the NSC staff varying levels of autonomy and influence over other agencies such as the Departments of State and Defense. President Dwight D. Eisenhower, for example, used the NSC meetings to make key foreign policy decisions, while John F. Kennedy and Lyndon B. Johnson preferred to work more informally through trusted associates. Under President Richard M. Nixon, the NSC staff, then headed by Henry A. Kissinger, was transformed from a coordinating body into an organization that actively engaged in negotiations with foreign leaders and implementing the President's decisions. The NSC meetings themselves, however, were infrequent and merely confirmed decisions already agreed upon by Nixon and Kissinger.
The National Security Council (NSC) is the main forum for collective discussion of the government's objectives for national security and about how best to deliver them in the current financial climate. A key purpose of the Council is to ensure that ministers consider national security in the round and in a strategic way.