Crossbow was the code name in World War II for Anglo-American operations against the German long range reprisal weapons (V-weapons) programme. The primary V-weapons were the V-1 flying bomb and V-2 rocket, which were launched against Britain from 1944 to 1945 and used against continental European targets as well.
Initial intelligence investigations in 1943 into the progress of German long range weapons were carried out under the code name Bodyline. On 15 November, a larger operation was set up under the name Crossbow. Post-war, Crossbow operations became known as "Operation Crossbow" particularly following the 1965 film of the same name.
Crossbow included strategic operations against research and development of the weapons, their manufacture, transportation and attacks on their launch site, and fighter intercepts against missiles in flight.
At one point, the British government, in near panic, demanded that upwards of 40% of bomber sorties be targeted against the launch sites.
The Crossbow attacks were not very successful, and every raid carried out against a V-1 or V-2 reduced the assets available for targets in the Third Reich. The diversion of Allied resources from other targets represented a major success for Hitler.
In May 1943 Allied surveillance observed the construction of the first of eleven large sites in northern France for secret German weapons, including six for the V-2 rocket. In November it discovered the first of 96 "ski sites" for the V-1 flying bomb.
Officials debated the extent of the German weapons' danger; some viewed the sites as decoys to divert Allied bombers, while others feared chemical or biological warheads. The Allies received detailed information about V-1, V-2 and Peenemünde research site from the Austrian resistance group around the priest Heinrich Maier. This also included the production sites such as the Raxwerke. When reconnaissance and intelligence information regarding the V-2 became convincing, the War Cabinet Defence Committee (Operations) directed the campaign's first planned raid (the Operation Hydra attack on Peenemünde in August 1943).
The works in France were the German "Site System 1" which was to be 96 fixed launching sites with storage bunkers (the 'ski' shapes) and outdoor ramps. Site System 2 (a reserve) and System 3 were planned. There were also four larger Wasserwerk ("Waterworks") bunker sites: Siracourt, Lottinghen, Couville, Tamerville, and Brécourt. Intended for use in January 1944 actual progress in construction, training and supply of V-1s was behind when inspected by German high command in October. French reports and detailed aerial reconnaissance linked with reconnaissance of Peenemünde indicated possibility of 2,000 missiles per day against England. Over half the sites were completed by December but Allied intelligence had identified all 96 by end of January. The first bombing of sites was by USAAF Martin B-26 Marauder medium bombers in early December with RAF Bomber Command starting night-time attacks shortly after but the greater inaccuracy of night bombing against small targets led the Joint Chiefs of Staff to use US heavy bombers in daylight. By the end of December, 54 sites had been attacked and 7 were destroyed. The bombing continued, and by end of March, 9 sites were destroyed and 35 seriously damaged. By May, 24 sites were destroyed and 58 seriously damaged.
Following Operation Hydra, a few Crossbow attacks were conducted on the "Heavy Crossbow" bunkers of Watten (V-2) and Mimoyecques (actually V-3 rocket cannon) from August and November 1943 respectively. "Crossbow Operations Against Ski Sites" began on 5 December with the "Noball" code name used for the targets (e.g., 'Noball 27' was the Ailly-le-Vieux-Clocher [sic] site, "Noball No. 93" was in the Cherbourg area, "Noball No. 107" was at Grand Parc, and "Noball V1 site No.147" was at Ligescourt).
The US formed its own Crossbow Committee under General Stephen Henry (New Developments Division) on 29 December 1943, and the US subsequently developed bombing techniques for ski sites in February/March 1944 at the Air Corps Proving Ground.
A mid-1944 plan for US Marine Corps aircraft to attack V-1 launch sites from aircraft carriers fell victim to inter-service rivalry – being opposed by the Army.
V-2 facilities were also bombed in 1944, including smaller facilities such as V-2 storage depots and liquid oxygen plants, such as the Mery-sur-Oise V-2 storage depot on 4 August 1944, and, by the Eighth Air Force, which bombed five cryogenic liquid oxygen plants in Belgium on 25 August 1944, but aborted the next days attack on plants "at La Louviere, Torte and Willebroeck, Belgium" due to cloud.
At the request of the British War Cabinet, on 19 April 1944, General Eisenhower directed Crossbow attacks to have absolute priority over all other air operations, including "wearing down German industry" and civilian morale "for the time being", which he confirmed after the V-1 assault began on the night of 12/13 June 1944, saying to Arthur Tedder "with respect to Crossbow targets, these targets are to take first priority over everything except the urgent requirements of the Overlord [invasion of Normandy] battle; this priority to obtain until we can be certain that we have definitely gotten the upper hand of this particular business".
The launches surprised the Allies, who had believed that the earlier attacks on the sites had eliminated the danger. The British, who had not expected German bombing of Britain to resume so late in the war, were especially upset. Some suggested using gas on the launch sites, or even executing German civilians as punishment.
Carl Spaatz, commander of US Strategic Air Forces in Europe (USSTAF), responded on 28 June to "complain that Crossbow was a 'diversion' from the main task of wearing down the Luftwaffe and bombing German industry" for the Combined Bomber Offensive, and to recommend instead that Crossbow be a secondary priority since "days of bad weather over Germany's industrial targets would still allow enough weight of attack for the rocket sites and the lesser tactical crises". By 10 July, Tedder had published a list of Crossbow targets which assigned 30 to RAF Bomber Command, 6 to the tactical Allied Expeditionary Air Force, and 68 to Spaatz's USSTAF; after which Spaatz again complained, so Eisenhower allowed "spare" bombing of non-Crossbow targets: "Instructions for continuing to make Crossbow targets our first priority must stand, but ... when ... the entire strategic forces cannot be used against Crossbow, we should attack – (a) Aircraft industry, (b) Oil, (c) Ball bearing (German): kugellagerwerke, (d) Vehicular production" (Eisenhower, 18 July).
Over a quarter of the Combined Bomber Offensive's tonnage of bombs were used against V-weapon sites in July and August; many of the attacks were ineffective, as they were against unused sites rather than the launchers themselves. Spaatz unsuccessfully proposed that attacks concentrate on the Calais electrical grid, and on gyrocompass factories in Germany and V-weapon storage depots in France. The gyrocompass attacks, along with targeting liquid oxygen tanks (which the Allies knew the V-2 needed), might have been very effective against the missiles. On 25 August 1944, the Joint Crossbow Target Priorities Committee (established 21 July) prepared the "Plan for Attack on the German Rocket Organization When Rocket Attacks Commence" – in addition to bombing of storage, liquid-oxygen, and launch sites; the plan included aerial reconnaissance operations.
Following the last V-1 launch from France on 1 September 1944, and since the expected V-2 attacks had not begun, Crossbow bombing was suspended on 3 September and the campaign against German oil facilities became the highest priority.
The V-1 threat from occupied France ended on 5 September 1944, when the 3rd Canadian Infantry Division contained the German military units of the Nord-Pas de Calais area, with their surrender following on 30 September.