Operation Crossbow - Heavy Sites - Siracourt

The 'Heavy Sites' were the large bomb proof installations in northern France associated with the German V Weapon programme.
 
In addition to firing V1s from the Bois Carré type installations, from the outset the Germans had planned to build large bomb proof facilities for their storage, assembly and launch. These sites had been spotted in 1943 because they were major rail-served constructions. After V1s had been assembled at Siracourt, they were fired from inside the bunker along a ramp which pointed to London, 130 miles away.