The Atlantic Wall is the most gigantic defensive military engineering undertaking since the Great Wall of China. Its construction was decided by Hitler from the spring of 1942, following the failure of his lightning offensive against the USSR. This set of discontinuous fortifications was intended to protect him from a coastal attack. From the Netherlands to the Pyrenees, it included 8,000 casemates, an artillery battery every 1.2 miles (2 km), an uninterrupted line of cheval-de-frise on each beach, radars and command posts every 12 miles (20 km), and bases for submarines in Brest, Lorient, Saint-Nazaire, La Pallice, and Le Havre. The Atlantic Wall was also dotted with 700 different models of blockhouses designed so as not to leave any blind spot.