 By the end of February 1943 , Đurišić 's Chetniks were resisting Partisan attempts to move east from the Neretva river . After the Battle of Neretva , during which the Partisans forced a crossing of the river against faltering Chetnik opposition , Đurišić 's detachment of about 2 @,@ 000 fighters fell back to Kalinovik , where they were almost defeated by the Partisan 2nd Proletarian Division in late March . Falling back further towards the Drina river , Đurišić had assembled about 4 @,@ 500 Bosnian and Montenegrin Chetniks around Foča by April but was in desperate need of supplies . Shortly after this , the Italians withdrew most of their troops from Foča and abandoned most of the Sandžak . For the rest of April 1943 , Đurišić fought a holding action against the Partisans along the Drina river with his 3 @,@ 000 remaining fighters . 
