Military doctrine
According to it, any citizen who resists an aggressor is a member of the armed forces, thus the whole population could be turned into a monolithic resistance army.
Starting from the elementary school education, over high schools, universities, organizations and companies, the authorities prepared the entire population to contest an eventual occupation of the country and finally to liberate it. For this purpose, the Territorial Defense Forces (TO) would be formed to mobilize the population in case of an aggression. The combat readiness of the TO meant that the steps of organization and training could be bypassed after the start of hostilities. The TO would supplement the regular Yugoslav People's Army, giving it greater defensive depth and an armed local population ready to support combat actions. Large numbers of armed civilians would increase the cost of an invasion to a potential aggressor.
The most likely scenario in the doctrine being used was a general war between the NATO and the Warsaw Pact. In such a situation, Yugoslavia would remain non-aligned, and it would not accept foreign troops of either alliance on its territory. The doctrine recognized the likelihood that one side or the other might try to seize Yugoslav territory as a forward staging area, to ensure lines of communication or simply to deny the territory to enemy forces. Such action would be considered aggression and would be resisted. Regardless of ideology, the occupiers would be considered Yugoslavia's enemy.

Territorial Defense Forces: The Territorial Defense Forces (TO) were formed in 1969 as an integral part of the Yugoslav Total National Defense doctrine. The TO forces consisted of able-bodied civilian males and females. Between 1 and 3 million Yugoslavs between the ages of 15 and 65 would fight under TO command as irregular or guerrilla forces in wartime. In peacetime, however, about 860,000 TO troops were involved in military training and other activities.
The TO concept focused on small, lightly armed infantry units fighting defensive actions on a familiar local terrain. A typical unit was a company-sized detachment. More than 2000 communes, factories, and other enterprises organized such units, which would fight in their home areas, maintaining local defense production essential to the overall war effort. The TO also included some larger, more heavily equipped units with wider operational responsibilities. The TO battalions and regiments operated in regional areas with artillery and antiaircraft guns and some armoured vehicles. Using their mobility and tactical initiative, these units would attempt to alleviate the pressure of enemy armored columns and air strikes on smaller TO units. In the coastal regions, TO units had naval missions. They operated some gunboats in support of navy operations. They were organized to defend strategic coastal areas and naval facilities against enemy amphibious landings and raids. They also trained some divers for use in sabotage and other special operations.
The TO was helped by the fact that most of its citizen-soldiers were one-time JNA conscripts who had completed their term of compulsory military service. However, TO recruitment was somewhat limited by the army's desire to include as many recently released conscripts as possible in its own military reserve. Other sources of TO manpower lacked prior military service and required extensive basic training.
The TO organisation was highly decentralized and independent. TO units were organized and funded by the governments in each of the Yugoslav constituent republics: Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia and Slovenia.

See also: Strategy
Grand strategy
Naval strategy
Operational level of war
Military strategy
Principles of war
Military tactics
Foreign policy doctrine
Military science

References: 

Bibliography: Chapman, Bert (2009), Military Doctrine: A Reference Handbook, ABC-CLIO, ISBN 9780313352331, retrieved 2021-04-16
Austin Long. The Soul of Armies: Counterinsurgency Doctrine and Military Culture in the US and UK. Ithaca–London: Cornell University Press, 2016.
NSA, (NATO STANDARDIZATION AGENCY) (2013), AAP-6(V) NATO Glossary of Terms and Definitions (PDF), archived (PDF) from the original on 2018-07-18, retrieved 2021-04-16
Christopher P. Twomey. The Military Lens: Doctrinal Difference and Deterrence Failure in Sino-American Relations. Ithaca–London: Cornell University Press, 2010.
History
Robert M. Cassidy. Peacekeeping in the Abyss: British and American Peacekeeping Doctrine and Practice after the Cold War. Westport, CT–London: Praeger, 2004.
Aaron P. Jackson. The Roots of Military Doctrine: Change and Continuity in Understanding the Practice of Warfare. Fort Leavenworth, KS: Combat Studies Institute Press, 2013.
Elizabeth Kier. Imagining War: French and British Military Doctrine between the Wars. Princeton: Princeton University Press, 1998 (reprint 2017).
Matthias Strohn. The German Army and the Defence of the Reich: Military Doctrine and the Conduct of the Defensive Battle 1918-1939, 2nd revised edn. Cambridge: Cambridge University Press, 2017.
Soviet
Willard C. Frank and Philip S. Gillette, eds. Soviet Military Doctrine from Lenin to Gorbachev, 1915-1991. Westport, CT: Greenwood Press, 1992.
Raymond L. Garthoff. Deterrence and the Revolution in Soviet Military Doctrine. Brookings Institution Press, 1990.
Odom, William E. (1988). "Soviet Military Doctrine". Foreign Affairs. 67 (2): 114–134. doi:10.2307/20043776. JSTOR 20043776.
Harriet Fast Scott and William F. Scott. The Armed Forces of the USSR. Boulder, Co.: Westview Press, 1979.
Harriet Fast Scott and William F. Scott. Soviet Military Doctrine: Continuity, Formulation, and Dissemination. Boulder, Co.: Westview Press, 1989.

External links: 
Joint Electronic Library
UK Development, Concepts and Doctrine Centre
Navy Warfare Development Command (NWDC)
Military Analysis Network
Air War College accessed September 27, 2006 – literally thousands of online texts and links to off-site sources
Quadrennial Defense Review Report. September 30, 2001 Archived December 25, 2016, at the Wayback Machine
US Military Doctrine since the Cold War accessed June 24, 2009
Fred Kaplan "The Doctrine Gap. Reality vs. the Pentagon's new strategy."
Pentagon Rethinking Old Doctrine on 2 Wars- The New York Times, March 14, 2009.
Joint Doctrine Ontology: A Benchmark for Military Information Systems Interoperability, Semantic Technology for Intelligence, Defense and Security, 2015