One of the first purpose built units to use Fw 190s in this role was "Stab/Versuchskommando Herrmann", a unit specifically set up in April 1943 by Major Hajo Herrmann. Herrmann's unit used standard A-4s and A-5s borrowed from day fighter units to intercept bombers over or near the targeted city, using searchlights and other visual aids to help them find their quarry. The first use of "Window" by the RAF during the Battle of Hamburg in July 1943, rendered the standard nightfighter "Himmelbett" procedures useless and brought urgency to the development of Herrmann's "Wilde Sau (Wild Boar)" technique, pending the development of new nightfighting strategies. Instead of restricting the Fw 190s to ground control interception protocols, the Fw 190s were given a free hand to over-fly bombed areas to see if they could locate bombers using the ground fires below. These tactics became an integral part of the nightfighter operations until May 1944.