 Complete the following phrase:  In January and February 1943, while under the overall command of Major Pavle Đurišić, Captain Lukačević and his Chetniks participated in several massacres of the Muslim population of Bosnia, Herzegovina and the Sandžak. Immediately after this, Lukačević and his Chetniks participated in one of the largest Axis anti-Partisan operations of the war, Case White, where they fought alongside Italian, German and Croatian NDH troops. The following November, Lukačević concluded a formal collaboration agreement with the Germans and participated in a further anti-Partisan offensive, 