Night Fighters
The Bf 110 would be the backbone of the Nachtjagdgeschwader throughout the war. The first units undertook defence operations over Germany as early as the autumn of 1940. Opposition was light until 1942, when British heavy bombers started to appear.
One of the most notable actions of the Bf 110 occurred on the night of the 17/18 August 1943. Some Bf 110 units had been equipped with the experimental Schräge Musik system, an emplacement of two upward-firing cannon, which for its initial installations placed the twin-cannon fitment almost midway down the cockpit canopy behind the pilot, which could attack the blind spot of RAF Bomber Command's Lancaster and Halifax bombers, which lacked a ventral turret. Using this, NJG 5's Leutnant Peter Erhardt destroyed four bombers in 30 minutes. Despite excellent visibility, none of the RAF bombers had reported anything unusual that would indicate a new weapon or tactics in the German night fighter force. This ignorance was compounded by the tracerless ammunition used by the Bf 110s, as well as firing on the British bombers blind spots. Many RAF crews witnessed a sudden explosion of a friendly aircraft, but assumed, in some cases, it was very accurate flak. Few of the German fighters were seen, let alone fired on. Later on, as the specialist Bf 110G-4s were received by night fighter wings, the mid-cockpit mount was replaced by one at the extreme rear of the cabin.

Messerschmitt Bf 110G-4 Schräge Musik installation.
During the Battle of Berlin, 1,128 bombers were lost in five months. RAF Bomber Command had "nearly burned out". These losses were primarily a result of fighter defences, at the heart of which was the Bf 110. The German defences had won a victory which prevented deep penetration raids for a time. But Luftwaffe losses were high; 15% of crews were killed in the first three months of 1944.
Most of the German night fighter aces flew the Bf 110 at some point during their combat careers, and the top night fighter ace of all time, Major Heinz-Wolfgang Schnaufer, flew it exclusively and claimed 121 victories in 164 combat missions.
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Wikipedia - BF 110