A service at Liverpool Cathedral has been held to honour those killed in The Battle of the Atlantic as part of a weekend of events commemorating the longest continuous military campaign in World War II.
The Battle of the Atlantic was vital in keeping supplies moving across the ocean to Britain from the United States and Canada.
The service, attended by the Princess Royal, was followed by a march to remember those who lost their lives during the battle for control of vital supply routes, beginning as war broke out in 1939.
The BBC reports Liverpool was the destination of many wartime Atlantic convoys and home of the Western Approaches Command.
The climax of the battle was in May 1943, when Germany's submarine fleet suffered heavy losses in the Atlantic.
Skirmishes in the Atlantic continued until the war ended in 1945, but the Allies sank particularly large numbers of U-boats in May 1943, effectively winning the Battle of the Atlantic.
Ships from the Royal Navy and around the world are converging on Liverpool for the commemorations.
Among those laying wreaths at the service was submarine Captain Patrick Walker, whose grandfather Captain Johnnie Walker was a national hero for his relentless pursuit of U-Boats in World War II.