The mountains of Zelengora were not part of the frontline during the 1990-1995 conflict and therefore have virtually no contamination with land mines and unexploded ordnance. Earlier though, in 1943, Zelengora became the scene of fierce combat during the Second World War, especially in a decisive phase of the Battle of the Sutjeska. By means of an operation called Fall Schwarz, the German occupational forces tried to encircle and destroy the YNLA, the partisan forces of Marshal Josip Broz Tito who had taken positions around Durmitor mountain in present Montenegro. Tito planned to break out of the encirclement towards the north across the river Sutjeska. In a battle that started on 5 June 1943, Partisan units of the YNLA 2nd Dalmatian Brigade took up positions in order to enable an escape of the YNLA forces through Zelengora. They were engaged by the German 118th Jäger Division. In spite of exhaustion, illness and dwindling munition supplies, the partisans of the 2nd Dalmatian Brigade held out against the far superior German forces until they were strengthened by the 1st Majevica Brigade on 9 June and were enabled to retreat in order to join the YNLA on 10 June. By that time, the 2nd Brigade had lost two thirds of its numbers, but had been successful in stalling the German advance sufficiently to allow Tito's forces to cross the Sutjeska river and break out of the German encirclement.