3-39. Foreign internal defense is participation by civilian and military forces of a government or international organizations in any of the action programs and activities undertaken by a host-nation government to free and protect its society from subversion, lawlessness, insurgency, terrorism, and other threats to its security (JP 3-22). Foreign internal defense involves all instruments of national power. Primarily a series of programs, it supports friendly nations operating against or threatened by hostile elements. Foreign internal defense promotes regional stability by helping a host nation respond to its population’s needs while maintaining security. Participating Army forces normally advise and assist host-nation forces while refraining from combat operations. Military necessity determines if U.S. forces train host-nation security forces under a foreign internal defense. Necessity increases when negative cultural and social consequences affect host nation security forces and their relationships with indigenous populations. USG support normally requires a host nation to positively apply the rule of law and legitimate governance.