Military history is often considered to be the history of all conflicts, not just the history of proper militaries. It differs somewhat from the history of war with military history focusing on the people and institutions of war-making while the history of war focuses on the evolution of war itself in the face of changing technology, governments, and geography. Military history has a number of purposes. One main purpose is to learn from past accomplishments and mistakes so as to more effectively wage war in the future. Another is to create a sense of tradition which is used to create cohesive military forces. Still another may be to learn to prevent wars more effectively. Armed forces may be organized as standing forces (e.g. regular army), 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 army) is only mobilized 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.

Military science concerns itself with the study and of the diverse technical, psychological, and practical phenomena that encompass the events that make up warfare, especially armed combat. It strives to be an all-encompassing scientific system that if properly employed, will greatly enhance the practitioner's ability to prevail in an armed conflict with any adversary

Military justice, as in the Uniform Code of Military Justice. Most nations have a separate code of law which regulates both certain activities allowed only in war, as well as provides a code of law applicable only to a soldier in war (or 'in uniform' during peacetime).

Military force is a term that might refer to a particular unit, a regiment or gunboat deployed in a particular locale, or as an aggregate of such forces (Example: "In the Gulf War the United States Central Command controlled military forces (units) of each of the five military services of the United States.")