The Macedonian people from the Pirin part of Macedonia actively participated in the National Liberation and the Anti-fascist movement. Since June 1941 the Local Committee of the Communist Party of Bulgaria (BKP) for Pirin Macedonia has taken the attitude concerning the armed struggle, especially being advocated by Nikola Parapunov, the secretary of the Local Committee. The first partisan group in the Pirin part of Macedonia was founded by Ivan Kozarev. This group performed the first anti-fascist action not only in Macedonia and Bulgaria, but also on the entire Balkan. The partisan groups were also founded by N. Parapunov and K. Kantardjiev. Taking into consideration the swift development of the partisan movement, the reprisals on the great number of Macedonians - anti-fascists have been made by the Bulgarian fascist government.
In 1942, the partisan movement has been developed. In the districts of Gorna Djumaja, Nevrokop and Petrich partisan companies have been founded. In 1943, the detachment "Jane Sandanski" and the detachment of Gorna Djumaja "Nikola Krapchev" were founded. These detachments executed some military actions. At the end of 1943 the movement suffered terrible stroke after the assassination of N. Parapunov and A. Pandurski.
In 1944, the partisan detachments in Pirin Macedonia founded the IV Insurrection Operative Zone and the brigade "Jane Sandanski". During the same year the units were enlarged in number. Considering the partisan movement connections with the Committees of the Liberation Front (OF) of Bulgaria, it also maintained the connections with the movement in the Vardar and the Aegean part of Macedonia. the combatants of the "Jane Sandanski" brigade should have to participate in the National Liberation War of Macedonia, but, soon after the foundation, the brigade was disbanded and the combatants joined the Bulgarian anti-fascist and the movement. The decisions being made at the I Session of ASNOM, at which participated the representatives from the Pirin part of Macedonia, have been accepted by the respective population. The wish for the union with Democratic Federal Macedonia has always been present in Macedonians from this part of Macedonia.
At the I legal Conference of the Bulgarian Labour Party (communists) BRP (k.), Gorna Djumaja District (5th and 6th of November, 1944) the attitude was assumed that the district is, by all means, in geographical, economic and ethnic sense the indivisible part of Macedonia. participating in the Anti-fascist war, the Macedonians from the Pirin part of Macedonia have nourished a hope that after the war the national and political rights will be recognized and guaranteed by the Bulgarian state.
At the end of the war, the leaders of Yugoslavia and Macedonia started negotiations with the leaders of Bulgaria concerning the establishment of the two countries federation (the Yugoslav proposal being a plural one, while Bulgarian being a dualistic one) at the same time advocating the union of the Pirin part of Macedonia with Democratic Federal Macedonia.