[1] It was formed by the outlawed Croatian Communist Party in the Independent State of Croatia established on 10 April 1941, in the Brezovica Forest near Sisak (in today's Croatia) on 22 June 1941, the day Germany invaded the Soviet Union.

It had 79 members, mainly Croats with the exception of one notable Serb woman, Nada Dimić,[1] and was commanded by Vladimir Janjić-Capo.

This event marked the start of armed anti-fascist resistance in occupied Yugoslavia.

In modern Croatia, 22 June is commemorated as a public holiday — the Anti-Fascist Struggle Day.

The detachment began resistance activities the day after its creation;[2] launching sabotage and diversionary attacks on nearby railway lines, destroying telegraph poles, attacking municipal buildings in surrounding villages, seizing arms and ammunition and creating a Communist propaganda network in Sisak and nearby villages.