"The fight against drugs is characterized by a progressive militarization of the issue, as seen by the various interventions, military agreements on no fly zones, strong investments in the armed forces (especially in South America, e.g. Colombia). The drug issue was in fact considered to be a national security issue by the US, in the framework of the Low Intensity Conflict theory elaborated by Pentagon in the 1980’s. President Reagan officially added drug trafficking to the list of threats to national security with his secret directive number 221, signed on April 1986. [22] This directive authorized the US military to intervene abroad in order to fight against drug production."

Source

Corti, Daniela and Swain, Ashok, "War on Drugs and War on Terror: Case of Afghanistan," Peace and Conflict Review (San Jose, Costa Rica: University for Peace, 2009) Volume 3, Issue 2, p. 3.
http://www.review.upeace.org/…