[2][3] After the war, concerned over both the strategic influence of the alliance between the newly reconstituted Poland and France and rumours of Polish construction of border fortifications, Rowehl began flying a hired private plane in his free time and photographing from 13,000 feet (4,000 m) to evade detection.

[4][5] He showed the photographs to the Abwehr, Germany's military intelligence department, and in 1930 was placed on the payroll, sometimes flying along the border with Poland and sometimes penetrating Polish airspace.

[6] From this one-man restart of German strategic aerial reconnaissance,[7] by 1934, Rowehl's operation had expanded to five aircraft and a small group of hand-picked pilots based at Kiel, and he had re-enlisted in the military as an officer.

[6][8] After the signing of the German–Polish Non-Aggression Pact in 1934 the unit went underground as the Experimental Post for High-Altitude Flights, purportedly investigating weather,[9] and moved to Berlin, flying out of the Staaken airfield.

[6] In 1936, at Göring's invitation, Rowehl's unit was transferred to the Luftwaffe, where it became the Squadron for Special Purposes, under the General Staff of the 5th Branch (intelligence).

The main units involved were the high-altitude Junkers Ju 86, Heinkel He 111, and Dornier Do 217, which could fly so high as to be invulnerable to interception by Soviet fighters.

Despite two Ju 86s being forced to land in the Soviet Union largely intact, with exposed cameras and film, Stalin did not register any protest.