The prevailing attitude to night fighting left commanders on the ground to carry out research on their own; the first occurred in Berlin, by Luftkreiskommando II from May to November 1936. The Oberkommando der Luftwaffe ordered experimenting with searchlights and aircraft from the summer, 1937. In 1939 several night fighter staffeln (squadrons or flights) had been established; but all of these had been converted back to day fighter units by 16 August 1939.[2]