Convoy routes, radar, and command control

Coastal trade convoys exposed ships to attack, but they also forced an attacker toward routes selected and organized by Britain. Because the Royal Navy scheduled those convoys, it knew where German craft would have to seek their targets. The remaining constraint was whether enough British vessels could cover the danger areas. Radar improved detection, while command-and-control frigates entering service from 1943 helped direct larger groups of small craft. E-boats were one part of a broader German coastal-force problem that also included R-boats and other vessel types.