180 Rose turrets were fitted to Lancasters before the end of the war, mainly in 1 Group but some to 5 Group.
Bomber Command recognised that the .303 was inadequate by 1942 and wanted a twin 20mm canon mid upper turret and a twin .5 calibre Browning one to the rear. The Air Ministry design program was slow (neither reached wartime installation) so a frustrated Arthur Harris, with the threat of political cancellation of his Berlin and Ruhr bombing campaigns due to the nightly loss of dozens of aircraft and hundreds of aircrew. approached private industry in 1943.
The Rose Brothers refused MAP assistance and took advice from Air Vice Marshall Edward Rice, a senior Bomber Command Station commander who subsequently led 1 Group. Initial problems with poor quality base rings overcome, the turrets started to be fitted to 101 Squadron aircraft from May 1944 (before final design approval). The guns suffered from frequent stoppages due to belt feed problems but the roomy design and improved visibility resulted in threats being spotted sooner allowing evasive action to be taken.
101 Squadron was switched to the ECM mode in October 1943 with new Lancasters fitted with 'Airborne Cigar'. These had high powered transmitters and an extra German speaking crew member who searched the night fighter radio channels. Interference and confusing commands were then broadcast. 101 aircraft went out virtually every night spaced along the bomber stream. The squadron grew to some 40 operational aircraft but lost some 145 as their broadcasts allowed fighters to home on them. Airborne Cigar was also fitted to 214 squadron B-17s and 462 Squadron Halifaxes.
The large numbers of downed bombers allowed the Germans to rapidly reinstate working examples of new defence and navigation aids and reverse engineer them to allow their fighters to detect and track allied aircraft. The RAF was horrified when a Ju 88G-1 landed at RAF Woodbridge (navigation error!) in July 1944 and was found to have detection equipment for both HS2 and Monica. The Germans were monitoring the HS2 pulses as the bomber stream formed up over England allowing them them to prepare their defence response although the aircraft based detector were not accurate enough to track individual aircraft. The rear facing Monica radar was supposed to alert the crew to fighters but could not differentiate between friend and foe so some turned it off to stop the constant beeping from other bombers in the stream. Those that didn't were giving out a tracking signal to enemy fighters resulting in many losses. Monica was removed whilst crews were instructed not to turn on HS2 until over occupied territory following the discovery..