The German threat
Copyright Imperial War Museum, reference Misc 51237
In 1939 the Kriegsmarine (German Navy) was not strong enough to risk a major battle with the Royal Navy, then the largest in the world. Instead Germany hoped to defeat Britain by attacking the ships that supplied her.
The Germans used submarines (U-boats), mines, surface warships, armed merchant ships and aircraft during the battle.
When the war started Germany had far fewer surface warships than Britain. Those they did have, however, were modern, powerful and fast. In the early war years they enjoyed great success in the Atlantic and elsewhere.
Aircraft such as the Focke-Wolf 'Kondor' or 'Kurier' operated out of occupied France from late 1940. They could fly hundreds of miles into the Atlantic. They directed U-boats on to convoys or bombed merchant ships. Fortunately for Britain, the Kriegsmarine never fully controlled the Luftwaffe (German Air Force). Nor did Germany's leader, Adolph Hitler, allow it to establish its own air force. As a result German air power was often directed elsewhere.
Thousands of mines were laid by U-boats, aircraft and surface ships around the British coast. Many ships were lost or damaged by these mines. Several ships were sunk or damaged in Liverpool Bay. Germany claimed that the port of Liverpool was forced to close by these activities but this was untrue.
All of these tactics were designed to cut Britain off from the rest of the world. But it was the U-boats that posed the deadliest threat to Britain's survival.