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Defending the lifeline

convoy of large ships

View from inside a North Atlantic convoy.
Image copyright Imperial War Museum

When the war began the Royal Navy, along with other Allied navies, took on the job of defending the merchant ships. The main method was the convoy system. This involved groups of merchant ships sailing in close formation under the protection of one or more escort warships.

The convoys originally consisted of up to 30 or 40 merchant ships in lines or columns. In later war years, Atlantic convoys became much larger, often exceeding 70 ships. At the outbreak of war the Navy was very short of ships suitable for convoy escort work. In September 1940 fifty old American destroyers were transferred to the British Navy. These old but sturdy ships did vital work escorting the convoys.

The development of 'escort groups' also proved an effective means of defence. They consisted of mixed types of small warships. They trained and worked together as a permanent team with common tactics. They were rigorously trained in anti-submarine tactics. These escort groups had many successes. In a ten-day period in 1941, four U-boats were sunk with the loss of three of Germany's top U-boat commanders.

The co-ordination of the convoys was under the control of 'Western Approaches Command'. Originally based in Plymouth, it moved to Liverpool, the largest and most central west coast port in 1941. There it became a vast organisation, responsible for the day-to-day direction of Britain's North Atlantic campaign.