'Beethoven' was the German programme to develop and use 'Mistel' (mistletoe) composite aircraft for the destruction of point targets (1941/45).

The scheme was based on the use of war-weary bomber airframes (initially those of Junkers Ju 88 twin-engined machines) with their forward sections packed with explosive. The 'Mistel' conversion was controlled from take-off to final dive onto the target by a fighter mounted above its fuselage on struts: after setting the converted bomber into its terminal dive onto the target, the fighter’s pilot released his machine from the struts and returned to base.

The first such composite machine flew in July 1943, and the first trials proved sufficiently encouraging for the Luftwaffe to allocate a high-priority test programme to Kampfgeschwader 200, its test unit. The technique was soon refined, and the bomber component, which was often a new aeroplane rather than a machine in the last stages of its operational utility, was fitted with a specialised 3,968-lb (1800-kg) warhead in a completely altered nose for maximum destructive effect on targets such as strategically important bridges.

The final stage of 'Mistel' development was the creation of purpose-built turbojet-powered bomber components, including types developed from the Messerschmitt Me 262 twin-turbojet fighter and Junkers Ju 287 four-turbojet bomber as well as the entirely new Arado E.377 twin-turbojet glide bomb. None of these latter schemes had reached fruition as hardware before the end of the war.

The definitive warhead for 'Mistel' bombers was a shaped charge based on a central core of copper or aluminium: the detonation of the explosive vapourised the metal and directed it in a supersonic and focused jet capable of penetrating up to 23 ft (7 m) of steel armour or concrete. It was anticipated that this would be able to 'drill' straight through a warship hull or destroy the foundation and/or pier of a major bridge.

Some 250 'Mistel' machines of various combinations were built, but these gained only limited success. The 'Mistel' was flown in combat for the first time against the Allied invasion fleet during 'Overlord', the primary target being the British-held harbour at Courseulles sur Mer. The 'Mistel' pilots claimed a number of hits, but none of these can be corroborated by Allied records, and may have been made against the hulk of the old French battleship Courbet, which had been included as a component of the 'Mulberry' harbour at Arromanches specifically as a decoy.

Serious blast and fragmentation damage from a near miss was also suffered by Nith, a 1,460-ton British 'River' class frigate converted as a floating headquarters, on 21 June: the ship suffered nine killed and 26 wounded. and had to be towed to back to southern England for repairs. A second opportunity to use the 'Mistel' concept, against British warships anchored in Scapa Flow during 1944, was abandoned after the loss of the German battleship Tirpitz assured local air superiority for the Royal Navy’s aircraft carriers.

As part of 'Eisenhammer' late in 1944, 'Mistel' aircraft were selected to carry out key raids against Soviet weapon-manufacturing capabilities and electricity-generating plants around Moscow and Gorky. These plants were known to be poorly defended and also irreplaceable. However, before the plan could be implemented, the Soviet army was already pushing into Germany itself and it was decided instead to use the 'Mistel' machines against the bridgehead at Küstrin.

On 12 April 1945 'Mistel' aircraft attacked the bridges being built there, but the damage caused was negligible and delayed the Soviet forces for only a day or two. Subsequent 'Mistel' attacks on other bridges being thrown over the Oder river by the Soviet forces were also ineffective.