 Within a week of Mihailović 's arrival the Partisans had successfully crossed the Neretva , and within another week they had forced the Chetniks to withdraw , losing Nevesinje then Kalinovik to the Partisans before the end of March . During the fighting , Chetnik commanders had been ill @-@ disciplined and had failed to cooperate , causing Ostojić to threaten them with courts martial and summary execution . Mihailović ordered Ostojić to pull the Chetniks back towards positions on the line of the Drina – Piva rivers , some 80 – 90 kilometres ( 50 – 56 mi ) southeast of Jablanica . By this point the Chetniks had suffered heavy losses , and the Partisans broke through the combined Italian – Chetnik defence line in early April . In a report dated November 1944 , Colonel S.W. " Bill " Bailey , the senior British liaison officer with the Chetniks during the war , stated that both Ostojić and Major Vojislav Lukačević had been very critical of Mihailović 's " foolhardy , though brave , tactical handling " of Chetnik forces during Case White , which had " contributed largely to the failure of operations " . However , Ostojić himself did not possess the necessary authority with his subordinate commanders , had been unable to cope with the rapidly changing situation , had adopted an unpopular and ineffective defensive strategy , and had then blamed the detachment commanders for the Chetnik failures . 
