The Germans soon gathered Come_together a large force and quelled Preventing_or_letting the uprising using mass terror , but the remaining Partisan forces crossed into Bosnia , where they formed the 1st Proletarian Brigade .

After Operation Trio , the Partisan leader Josip Broz Tito , his Supreme Headquarters and the Partisan main force , consisting of the 1st and 2nd Proletarian Brigades , withdrew Escaping from their base of operations around Foča .