The Territorial Defense or 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 2,000 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. But TO recruitment was somewhat limited by the JNA 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 was highly decentralized and independent. TO units were organized and funded by the governments in each of the Yugoslav constituent republics: SR Bosnia and Herzegovina, SR Croatia, SR Macedonia, SR Montenegro, SR Serbia and SR Slovenia, as well as in each of SR Serbia's subunits SAP Vojvodina and SAP Kosovo.

The possibility that each Yugoslav federal unit could have its own armed formations led to concerns that someday these separate "armies" might oppose the federal Yugoslav JNA in an act of an eventual secession.Such concerns became reality during the breakup of Yugoslavia and the Yugoslav Wars when the TO forces in many of the constituent republics switched their allegiance and turned into separatist paramilitaries. Those former TO forces, along with Yugoslav army deserters and volunteers contributed to the founding of the respective armies of the independent states and other political entities that emerged after the disintegration of Yugoslavia. This includes the armies of Bosnia and Herzegovina, Croatia, Macedonia, Montenegro, Serbia and Slovenia.