Armed forceAn Armed Force is formed for the defensive purpose of controlling territory or other economic resources, and/or for the offensive purpose of seizing the same from another entity. The study of the use of Armed Forces is called Military Science. Broadly speaking, this involves considering offense and defense at three "levels": strategy, operative art, and tactics. All of these areas study the proper application of the use of force in order to achieve a desired objective. Organization Armed forces may be organized as standing forces, which describes a professional army that is engaged in no other profession than preparing for and engaging in warfare. In contrast, there is the citizen army. A citizen army (also known as a militia or reserve) is only formed as needed. Its advantage lies in the fact that it is dramatically less expensive (in terms of wealth, manpower, and opportunity cost) for the organizing society to support. The disadvantage is that such a "citizen's army" is less well trained and organized. Historically, professional armies often triumph over much larger citizen armies when engaged in combat. A compromise between the two has a small cadre of professional NCOs (non-commissioned officers) and officers who act as a skeleton for a much larger force. When war comes, this skeleton is filled out with conscripts or reservists (former soldiers who volunteer for a small stipend to occasionally train with the cadre to keep their military skills intact), who form the wartime unit. This balances the pros and cons of each basic organization, and allows the formation of huge armies (in terms of millions of combatants), necessary in modern large scale warfare. Militaries in many larger countries are divided into an army, an air force, and a navy (if necessary). These divisions may be solely for the purposes of training and support, or may be completely independent branches responsible for conducting operations independently of other services. Most smaller countries have a single military that encompasses all armed forces employed by the country in question. Benefits and Costs The investment in military forces and their associated technologies can result in many ancillary benefits to the society as a whole. While the investment in a military is essentially consumptive (i.e. does not provide direct benefit to a societies infrastructure or productive means), this does not mean that these additional benefits have little value. These military investments are increased during a war or other conflict, and in a virtuous cycle can accelerate the technological development of the society as a whole. Conversely, over investment in military forces can drain a society of needed manpower and material, significantly impacting civilian living standards. If continued over a significant period of time, this results in reduced civilian research and development, degrading the overall societies ability to improve its infrastructure. This lack of development in turn effects the military in a vicious cycle. See the Soviet Union for a typical modern example of this problem. Militaries may also benefit their country by providing security from foreign and internal conflict. They may also harm a society by engaging in counter-productive (or merely unsuccessful) warfare, or by domestic repression.