Insurgency and its tactics are as old as warfare itself. Joint doctrine defines an insurgency as an organized movement aimed at the overthrow of a constituted government through the use of subversion and armed conflict (JP 1-02). Stated another way, an insurgency is an organized, protracted politico-military struggle designed to weaken the control and legitimacy of an established government, occupying power, or other political authority while increasing insurgent control. Counterinsurgency is military, paramilitary, political, economic, psychological, and civic actions taken by a government to defeat insurgency (JP 1- 02). These definitions are a good starting point, but they do not properly highlight a key paradox: though insurgency and COIN are two sides of a phenomenon that has been called revolutionary war or internal war, they are distinctly different types of operations. In addition, insurgency and COIN are included within a broad category of conflict known as irregular warfare.
Political power is the central issue in insurgencies and counterinsurgencies; each side aims to get the people to accept its governance or authority as legitimate. Insurgents use all available tools—political (including diplomatic), informational (including appeals to religious, ethnic, or ideological beliefs), military, and economic—to overthrow the existing authority. This authority may be an established government or an interim governing body. Counterinsurgents, in turn, use all instruments of national power to sustain the established or emerging government and reduce the likelihood of another crisis emerging.
Long-term success in COIN depends on the people taking charge of their own affairs and consenting to the government’s rule. Achieving this condition requires the government to eliminate as many causes of the insurgency as feasible. This can include eliminating those extremists whose beliefs prevent them from ever reconciling with the government. Over time, counterinsurgents aim to enable a country or regime to provide the security and rule of law that allow establishment of social services and growth of economic activity. COIN thus involves the application of national power in the political, military, economic, social, information, and infrastructure fields and disciplines. Political and military leaders and planners should never underestimate its scale and complexity; moreover, they should recognize that the "Armed Forces cannot succeed in COIN alone."