The term use of force describes a right of an individual or authority to settle conflicts or prevent certain actions by applying measures to either: a) dissuade another party from a particular course of action, or b) physically intervene to stop them. In nations of the developed world and the developing world, citizens allow police, corrections, or other security personnel to employ force to actively prevent imminent commission of crime, or even for deterrence. It may also be exercised by the executive branch (i.e., through the president, prime minister, premier, governor or mayor) of a political jurisdiction, deploying the police or military to maintain public order. The use of force is governed by statute and is usually authorized in a progressive series of actions, referred to as a "use of force continuum.
When a conflict is between parties having the same standing, observers often recommend the use of negotiation or other "conflict resolution" techniques. When a conflict is between a lawbreaker and a law enforcer, use of force comes into play when the lawbreaker refuses to desist, or attempts to flee from a serious offense. The continuum of force progresses from verbal orders, through physical restraint, up to lethal force. The general rule for application of force is that only necessary force may be used. When force is applied by an individual (for example, to protect life, or property), the amount of force permissible is, likewise, only that which is reasonable and necessary under the circumstances.
When a level of force beyond verbal commands is used, the individual or authority authorizing the force is accountable for the degree of force applied. In the case of lethal force, other levels of force must have been attempted first unless lethal force is the only way to minimize loss of life. When the use of military force is employed by the state towards another political entity for defensive purposes, international law requires that the principle of proportionality be applied.
Military and police
A use of force doctrine is employed by police forces, as well as soldiers on guard duty, to regulate the actions of police and guards. The aim of such a doctrine is to balance security needs with ethical concerns for the rights and well-being of intruders or suspects. In the event that members of the public are injured, this may give rise to issues of self-defense as a justification. In the event of death, this may be a justifiable homicide.
U.S. soldiers on guard duty are given a "use of force briefing" by the sergeant of the guard before being assigned to their post.
"The only difference between lawful force for police and civilians is that peace officers are not given the option of fleeing the scene to avoid confrontation." 
Indeed, soldiers on guard duty will be severely punished for "abandoning their post" if they leave before being "properly relieved".
For the English law on the use of force by police officers and soldiers in the prevention of crime, see Self-defence in English law. The Australian position on the use of troops for civil policing is set out by Michael Hood in Calling Out the Troops: Disturbing Trends and Unanswered Questions  and, for comparative purposes, see *Keebine-Sibanda, Malebo J. & Sibanda, Omphemetse S. "Use of Deadly Force by the South African Police Services Re-visited". .
Use of force continuum
The use of force may be standardized by a use of force continuum, which presents guidelines as to the degree of force appropriate in a given situation. One source identifies five very generalized steps, increasing from least use of force to greatest. It is only one side of the model, as it does not give the levels of subject resistance that merit the corresponding increases in force.
- Presence (using the effect of the presence of an authority figure on a subject)
- Verbalization (commanding a subject)
- Empty hand control (using empty hands to search, relieve weapons, immobilize, or otherwise control a subject)
- Intermediate weapons (using non-lethal chemical, electronic or impact weapons on a subject)
- Deadly Force (using any force likely to cause permanent injury or death to a subject)
Use of force continuums can be further broken down into much more specific and concrete units.
- The use of force is derived from British Common Law in English-speaking countries. It is a tradition of other legal systems, such as the French Civil Code  and is enshrined in international law 
- Commonwealth of Australia Reasonable and necessary force. Commonwealth Consolidated Acts. CRIMES ACT 1914 - SECT 3ZQI. Retrieved on: October 8, 2007.
- O'Connell, Mary Ellen (2007). "Proportionality and the Use of Force in the Middle East Conflict". Jurist: Legal News and Research. Bernard J. Hibbitts. http://jurist.law.pitt.edu/forumy/2006/07/proportionality-and-use-of-force-in.php. Retrieved 2007-10-07.
- Basic Principles on the Use of Force and Firearms by Law Enforcement Officials, Eighth United Nations Congress on the Prevention of Crime and the Treatment of Offenders, Havana, 27 August to 7 September 1990, U.N. Doc. A/CONF.144/28/Rev.1 at 112 (1990).