On 1 April 1934 a unit called the "Hanseatische Fliegerschule" e. V. was formed, initially based at Fassberg. This organisation was formed into a "Geschwader" (wing) and created as a Kampfgeschwader (battle or bomber wing) on 1 May 1939. The command "staffel" (squadron), or "Stab" unit, was created from KG 155, a defunct bomber unit on 1 May 1939. The organisation was created at Giessen aerodrome and was subordinated to "Luftflotte" 4 (Air Fleet 4). The "stab" staffel was placed under the command of Wilhelm Süssmann, who became the first "Geschwaderkommodore" of KG 55. The unit trained intensively over the spring and summer, 1939. On 31 August Süssmann was ordered to Wesendorf in preparation for an attack on Poland. The unit was equipped with the Heinkel He 111P-4 medium bomber.