The Royal Navy's 1939 problem was that its small-craft building programme had not yet produced the numbers it needed. Output began to spool up in 1940, became substantial in 1941 and 1942, and provided real numerical depth by 1943. One example has a single Dog Boat taking on six E-boats, whose armament included torpedoes and a single 37 mm Flak gun. Fairmile D Dog Boats and other British motor craft could accumulate 6-pounders, Bofors guns, aircraft cannon, engine modifications, and steel-reinforced bows. Some gun boats were converted to carry torpedoes for the invasion screen, creating more chances to stop a German destroyer quickly even if the ideal intercepting ship was absent. Their increasingly heavy armament and room for modification exceeded the narrower margins available aboard E-boats.
Chapter · 29:20-32:07
Mass-produced coastal craft and firepower
Britain's growing output let coastal forces add guns, engines, reinforced bows, and torpedoes while maintaining the numerical depth needed for D-Day.