This publication, "Foreign Internal Defense (Joint Publication 3-22)," establishes joint doctrine for the Armed Forces of the United States involved in or supporting foreign internal defense (FID). It discusses how joint operations, involving the application of all instruments of national power, support host nation efforts to build capability and capacity to free and protect its society from subversion, lawlessness, and insurgency. Foreign internal defense (FID) is the participation by civilian and military agencies of a government in any of the action programs taken by another government or other designated organization, to free and protect its society from subversion, lawlessness, insurgency, terrorism, and other threats to their security. The focus of US FID efforts is to support the host nation's (HN's) internal defense and development (IDAD), which can be described as the full range of measures taken by a nation to promote its growth and protect itself from the security threats. While historically, the United States provided notable, and largely unconditional, assistance to friendly foreign nations following World War II (Truman Doctrine and the Marshall Plan), FID as conducted today has its genesis in the post-Vietnam era when US policy shifted to emphasize that the United States would assist friendly nations, but would require them to provide the manpower and be ultimately responsible for their own national defense. It is important to frame the US FID effort within the context of the US doctrine it supports and to understand how it fits into the HN IDAD program. US military support to FID should focus on assisting an HN in anticipating, precluding, and countering threats or potential threats and addressing the root causes of instability. Emphasis on internal developmental programs as well as internal defense programs when organizing, planning, and executing military support to US FID activities is essential. Although the FID operation is considered military engagement, security cooperation, and deterrence, FID may include or support operations from across the range of military operations to support the HN's IDAD strategy. Accordingly, US military operations supporting FID provide training, materiel, advice, or assistance to local forces executing an IDAD program, rather than US forces conducting IDAD military missions for the HN. Military officials often have greater access to, and credibility with, HN regimes that are heavily influenced or dominated by their own military. However, the characteristics of FID involve the instruments of national power beyond the military instrument (diplomatic, informational, and economic) through which sources of US power (such as financial, intelligence, and law enforcement) can be applied to support an HN IDAD program. This publication has been prepared under the direction of the Chairman of the Joint Chiefs of Staff. It sets forth joint doctrine to govern the joint activities and performance of the Armed Forces of the United States in operations and provides the doctrinal basis for interagency coordination and for US military involvement in multinational operations while conducting or supporting FID. It provides military guidance for the exercise of authority by combatant commanders and other joint force commanders (JFCs) and prescribes joint doctrine for operations, education, and training. It provides military guidance for use by the Armed Forces in preparing their appropriate plans. It is not the intent of this publication to restrict the authority of the JFC from organizing the force and executing the mission in a manner the JFC deems most appropriate to ensure unity of effort in the accomplishment of the overall objectives. Joint doctrine established in this publication applies to the joint staff, commanders of combatant commands, subunified commands, joint task forces, subordinate components of these commands, the Services, and defense agencies in support of joint operations.