'Danny' was a US unrealised plan to use fighter squadrons of the US Marine Corps to attack V-1 flying bomb launch sites in northern France as part of 'Crossbow' (June/July 1944).
Shortly after the start of 'Overlord', the Germans began to launch V-1 weapons against a number of European cities and ports. The Allies responded with specialised anti-aircraft batteries firing proximity-fused projectiles, and fighters capable of high speed at low altitude. Moreover, as early as December 1943 General Dwight D. Eisenhower, the overall commander of the Allied forces in Europe, had ordered the start of 'Crossbow', which took the form of attacks on manufacturing and support facilities for the German rocket programme.
As part of the operation, in June 1944 the Naval Air Atlantic staff began the development of a scheme to make use of USMC fighter squadrons to attack the launch sites. This undertaking was allocated to the Vought F4U Corsair fighter-bomber units of Marine Air Group 51, including the VMF-511, VMF-512, VMF-513 and VMF-514 squadrons, which was to operate from escort carriers in the North Sea to attack V-1 flying bomb and V-2 ballistic missile sites in northern France with the 11.75-in (298-mm) 'Tiny Tim' unguided rocket.
In preparation for this undertaking, the MAG-51 squadrons were equipped with F4U-1 and F4U-1A warplanes, and started to train at MCAS Cherry Point, North Carolina. A detailed briefing on the operation was presented in July 1944 in the newly completed Pentagon building, but during this briefing the US Army chief-of-staff, General George C. Marshall, walked out, and this spelled the effective end of 'Danny', which had become a clear victim of inter-service rivalry.