The rise of General Ion Antonescu in Romania in 1940 led to a reorganization of his country's armed forces.

[2][5] Here, Süß joined the trio of Hermann Graf, Alfred Grislawski and Heinrich Füllgrabe.

On 21 June, the Gruppe was ordered to Mizil in preparation of Operation Barbarossa, the German invasion of the Soviet Union.

Its primary objective was to provide fighter protection for the oil fields and refineries at Ploiești.

[7] In the months following the beginning of Operation Barbarossa, the 9./JG 52, later dubbed the Karaya Quartet, became one of the most successful units of the Luftwaffe.

He claimed his first victory on 8 August 1941 and in the next twelve months, fighting in the Caucasus and the Battle of Stalingrad, Süß reached a series of victories against the Soviets, for which he was awarded the Honour Goblet of the Luftwaffe (Ehrenpokal der Luftwaffe) on 4 May 1942,[8] the German Cross in Gold (Deutsches Kreuz in Gold) on 29 June 1942.

[11] In the spring of 1943, Süß was transferred to the Ergänzungsgruppe Ost, where he remained a long time as an instructor.

In response to political humiliation caused by de Havilland Mosquito bombing raids into Germany, Reichsmarschall Hermann Göring, the commander-in-chief of the Luftwaffe, ordered the formation of two specialized high-altitude Luftwaffe units.

[12][13][14][15] Graf was permitted to choose his personnel and had his friends Süß, Füllgrabe and Grislawski transferred from III.

On 20 December 1943, the United States Army Air Forces (USAAF) bombed Bremen.