In 1991, the process of disintegration of the Socialist Federal Republic of Yugoslavia began. The former Socialist Republics of Croatia and Slovenia were the first to announce their secession from the Federation in the last days of June. To restore the constitutional order, units of the Armed Forces of the SFR of Yugoslavia were sent to Slovenia, which faced the armed resistance of the Slovenian Territorial Defense (TO RS or TOS). In the Ten-Day War, the Federal troops, despite their numerical and technical advantage, suffered a defeat in the confrontation with the TOS subunits. Decisive for the success of Slovenian actions turned out to be the right choice of method of operation, knowledge of the combat environment, as well as high morale and support provided by the civilian population. The example of the Ten-Day War, an analysis of its course, shows that with the appropriate use of the TOS forces, they can conduct an effective fight against operational troops and be a fully-fledged component of the Armed Forces.