In September 1943, United States Lieutenant Colonel Albert B. Seitz and Lieutenant George Musulin parachuted into the Territory of the Military Commander in Serbia, along with British Brigadier Charles Armstrong.
In early December 1943, Lukačević's Chetniks participated in Operation Kugelblitz, the first of a series of German operations alongside the 1st Mountain Division, 7th SS Volunteer Mountain Division Prinz Eugen, and parts of the 187th Reserve Division, the 369th (Croatian) Infantry Division and the 24th Bulgarian Division.