 Complete the following phrase:  III.JG 27 left Italy in late July to return to Vienna. The gruppe returned to the Mediterranean on 23 September, but located to Argos, near Athens in Greece; it remained engaged in combat operations in this theatre until March 1944. A fourth group was added to JG 27 in June. IV. Gruppe was created in Greece and placed under the command of Hauptmann Rudolf Sinner. This gruppe remained in action over Greece and the Balkans until March 1944. The Allied invasion of Italy, Operation Avalanche had considerable impact on JG 27 gruppen operating in southeast Europe. Allied air forces operating from Italy from September 1943, faced only the barrier of the Adriatic Sea. Allied bombers began to make frequent raids into the Axis-held Balkans until the end of the war. Among the JG 27 pilots to emerge in the air battles over Greece was Heinrich Bartels, drafted from Jagdgeschwader 5 after service in the Arctic Circle. In October 1943, III. Gruppe was left to cover Greece and Crete while IV. Gruppe moved to Podgorica, Yugoslavia. Later in October, elements of III. Gruppe flew combat operations over Corsica, and were based at Viterbo briefly. In combat over Serbia, IV. Gruppe doubled its total but lost their recently appointed commanding officer, the 188-victory ace Joachim Kirschner killed on 17 December. Kirschner was the second of groups commanders to die, after acting commander Dietrich Boesler. JG 27 flew in support of the 