protectorate of Albania. The prospect of British Empire support and the establishment of a second Allied foothold on the continent forced Hitler to assist Mussolini. Hitler developed Operation Marita, the German-led invasion of Greece with support from Romania, Hungary and Bulgaria. Yugoslavia refused to join the Axis powers, and the operation was expanded to include the country in German plans. Richthofen's air corps was given two wings of Ju 87s for the task; StG 2 and 3. Stab./StG 2 was moved to Kraynitsi, 42 km south-south west of Sofia, Bulgaria on 6 March 1941. Hitschhold's group, I./StG 2 followed on 27 March with 39 Stukas. II/StG 2 remained in Africa, but III./StG 2 under Brücker moved to Belica-North, 85 km south-south east of Sofia on 6 March. 35 of the 38 Ju 87s were available for combat operations on 6 April. The German invasion of Yugoslavia and the Battle of Greece commenced on 6 April. Richthofen's Ju 87s supported the German Twelfth Army in southern Yugoslavia, which cut the Yugoslav Army off from Greece and the Allied expeditionary forces there. The victory in Yugoslavia was complete with the bombing of Belgrade, which facilitated a rapid victory by destroying command and control centres. I./StG 2 dive-bombed Yugoslav force opposite Petrich and the Metaxas Line, and subsequent Battle of the Metaxas Line. It is not clear whether the group took part in the Belgrade bombing; it may have done. The group attacked British forces in Arta, and the advances on Skopje, Prilep, Veles and Salonika. The Stukas facilitated the breakthrough at the Battle of Lake Kastoria, and the battles at Olympia, Larissa, Volos and Battle of Thermopylae. They also supported the advances in Corinthia and Pelponisia. From 22 April they were operating in against shipping in the Megara Gulf. They also sank a number of ships in the Gulf of Corinth. III./StG 2 supported other units in the majority of the same battles. It flew combat missions against the Royal Yugoslav Air Force bases and notably assisted in the seizure of the Corinth Canal on 26 April. The attacks against shipping evacuating Allied forces from Greece were successful. Richhofen's airmen claimed 280,000 tons of shipping (60 vessels) destroyed up until 30 April 1941; the claims were approximately correct. Athens fell on 27 April and the bulk of mainland Greece was under Axis control by 30 April. Operation Demon—the Allied evacuation from Greece—succeeded;