 Once past the edge of Swiss territory, the bombers tracked south-west for the Italian Lakes.German night fighter airfields, and ground radar stations, were mainly concentrated in a defensive line across north-east France, the Low Countries, north-west Germany and Denmark.When the RAF raiders were reported at Friedrichshafen, 300–400 miles away, the Luftwaffe controller decided to marshal his fighters over the bases of Florennes, near Charleroi, and Juvincourt, near Reims, to catch the bomber force on its return.