 Complete the following phrase:  StG 77 then moved to the Balkans. It operated in the battle for the air superiority, anti-shipping, interdiction and close support role in the Invasion of Yugoslavia, Battle of Greece and Battle of Crete in April and May 1941. The wing inflicted heavy losses on shipping with StG 1, StG 2 and StG 3. StG 77 was supported Army Group Centre and Army Group South on the Eastern Front, from June 1941, after Operation Barbarossa. In particular, it served with distinction in the 