Power projection (or force projection) is a term used primarily in American military and political science to refer to the capacity of a state to implement policy by means of force, or the threat thereof, in an area distant from its own territory. The United States Department of Defense, in its publication J1-02: Department of Defense Dictionary of Military and Associated Terms, further defines power projection as The ability of a nation to apply all or some of its elements of national power - political, economic, informational, or military - to rapidly and effectively deploy and sustain forces in and from multiple dispersed locations to respond to crises, to contribute to deterrence, and to enhance regional stability. blank">http://www.dtic.mil/doctrine/jel/doddict/data/p/04138.html This ability is a crucial element of a state's _power in international relations. Any state able to direct its military forces outside the limited bounds of its territory might be said to have some level of power projection capability, but the term itself is used most frequently in reference to militaries with a worldwide reach (or at least significantly broader than a state's immediate area). Even states with sizable hard power assets (such as a large standing army) may only be able to exert limited regional influence so long as they lack the means of effectively projecting their power on a global scale. Generally, only a select few states are able to overcome the logistical difficulties inherent in the deployment and direction of a modern, mechanized military force.

While traditional measures of power projection typically focus on hard power assets (tanks, soldiers, aircraft, naval vessels, etc.), the developing theory of soft power notes that power projection does not necessarily have to involve the active use of military forces in combat. Assets for power projection can often serve dual uses, as the deployment of various countries' militaries during the humanitarian response to the 2004 Indian Ocean earthquake illustrates. The ability of a state to project its forces into an area may serve as an effective diplomatic lever, influencing the decision-making process and acting as a potential deterrent on other states' behavior.