The fortress was a military base for German secret weapons, destined to be launched on London. In Landrethun-le-nord, in a place called "Mimoyecques", a secret base was built underground.
It was intended to launch hundreds of V3 missiles per day on London. It was destroyed on 6 July with Tallboy bombs. Excavations have uncovered an entrance, and some of the shafts can be visited.
The V-3 Vergeltungswaffen was planned to bombard England, and more precisely London, its only target. But the lack of mobility of this kind of weapon made it extremely vulnerable to bombarding and air raids.
This is why it had to be contained in a fortified system. Five of these shafts were constructed in Mimoyecques, in the commune of Marquise in the Pas-de-Calais, along with an entire network of service shafts, tunnels and rooms on several levels, essential for troops staying there and for the many technical departments.
An interior railway line was even built to provide transport from one end to the other. On the surface, a particularly vulnerable zone, angled drifts opened onto a reinforced concrete slab 5. The openings in the slab were protected by 20 cm thick steel plate. The site was chosen due to its proximity to the target km from London , and also to it being set back from the coastline, to avoid any naval attacks.
