'Ski Site' was the Allied semi-official designation of the ramp sites in northern France and the Low Countries from which Oberst Max Wachtel’s Flakregiment 155(W) launched V-1 cruise missiles (12 June/5 September 1944).
Intelligence reports had informed the Allies of the existence and nature of the 'Ski Sites', and photo-reconnaissance first recorded the type in October 1943, allowing the preparation of the 'Noball' offensive that started on 5 December 1943 and ended on 1 July 1944 after more than 23,196 tons of bombs had been dropped on 96 'Ski Sites'. The campaign ended on 5 September 1944 when the reconnaissance regiment of the Canadian 3rd Division contained the German units in north-eastern France, these surrendering on 20 September.
To supply their V-1 flying bomb launch sites in the Calais region, the Germans began to construct several storage depots in August 1943, and of these the sites at Biennais, Oisemont Neuville au Bois and St Martin l’Hortier were not completed. Those which were completed were located at Domléger near Abbeville, which was bombed on 14 and 16 June, and on 4 July; Renescure near St Omer, which was finished in November 1943 and bombed by the USAAF on 16 June and 2 July 1944; and Sautricourt near St Pol, which was bombed 16 June. To serve the 10 launch sites planned for Normandy, a depot was constructed at Beauvais, and this was bombed 14, 15 and 16 June 1944. A depot to serve Cherbourg launches was sited near Valognes. By February/March 1944, a plan for three new underground V-1 storage sites was put into effect. The Nucourt limestone cave complex between Pontoise and Gisors was bombed on 22 June, and 298 V-1 missiles were buried or severely damaged. That in the Rilly la Montagne railway tunnel was attacked by the British with 'Tallboy' earthquake bombs on 31 July, both ends of the tunnel being collapsed. The St Leu d’Esserent mushroom caves constituted the largest of the underground V-1 sites, and this was attacked by the RAF’s No. 617 Squadron with 'Tallboy' bombs on 4 July. A larger 'Heavy Crossbow' bunker was built at Siracourt, between Calais and the Somme river as a V-1 storage depot. RAF records refer to flying bomb stores at Bois de Cassan (bombed on 2/4 August), the Forêt de Nieppe (bombed 24/25 July and 3/4 and 5/6 August) and Trossy St Maximin (bombed on 3/4 August).
The V-1 launch sites in France were located in nine general areas, four of them with their ramps aligned toward London, and the others toward Brighton, Dover, Newhaven, Hastings, Southampton, Manchester, Portsmouth, Bristol, and Plymouth. The sites on the Cherbourg peninsula targeting Bristol and Plymouth were captured before they could be used, and eventually launching ramps were moved to the Netherlands to target Antwerp, which was first attacked on 3 March 1945 from Delft.
At first the V-1 launch sites had storage buildings curved at the end to protect the contents against damage from air attacks. On aerial reconnaissance pictures these storage from above looked like snow skis ('ski sites'). An intelligence report of 28 October 1943 about construction at Bois Carré near Yvrench led to the launch of a photo-reconnaissance mission by the RAF’s No. 170 Squadron on 3 November, and this revealed 'ski-shaped buildings 240-270 feet long'. By November 1943, 72 of the ski sites had been located by Allied reconnaissance, and 'Crossbow' missions began to attack the original ski sites on 5 December 1943. The Germans later began to construct modified sites with limited structures that could be completed quickly, as and when required, and this also facilitated post-bombing repair. However, the work to complete a modified site before launching allowed Allied photographic interpreters to predict on 11 June 1944 that the V-1 attacks would begin within 48 hours, and the first attacks began on 13 June.