The << Atlantic Wall >>, built by the German forces along the occupied coasts of Western Europa as a rampart to protect them against Allied landing attempts, included a powerful chain of anti-naval and anti-air detection devices, which may be seen as a kind of counterpart to the British Chain Home. But its structure was quite different, and probably was most efficient at the time it was built. Today, 70 years later, remains of this continental chain can still be seen in many places, especially in France. Their <;<; archaeological >> study may enlighten the war time archives and documents from both sides, to explain how it was built, how it worked, and evaluate its supposed efficiency. The paper describes also the progressive discovery of this chain by the allies, which lead them to conceive a lot of counter-measures, which made it quite inefficient during the crucial days of June 44 in Normandy.

It is a common belief by many people that the resonant-cavity magnetron was invented in February 1940 by Randall and Boot from Birmingham University. In reality, this is not the full story. Rather, it is a point of view mostly advocated by the winners of the Second World War, who gained a great benefit from this microwave power tube (thanks to a two-orders-of-magnitude increase of power) in the Battle of the Atlantic, in night bombing until the final collapse of the German Reich, and in many other operations. This paper discusses the contributions by other nations, mainly France, but also Germany, Japan, The Netherlands, the Czech Republic, the USSR, and even more, to the cavity magnetron and to its roots.