The Forgotten Service

[David Fox]

Blue Star lost 38 ships of a total 381,000 gross tons and 646 Masters, Officers and men gave their lives in World War 2, out of a total of 30,000 Merchant Navy casualities caused by enemy action.
Taffrail BSL 1939- 1945

Merchant Seamen Deaths, 1939 -1953
This collection details the names of over 50,000 merchant seamen who lost their lives during and just after WWII. The Merchant Navy during this time was made up of approximately 185,000 seamen, including 40,000 men of Indian, Chinese and other nationalities.
When war broke out, the merchant fleet, which was the largest in the world, was put under the control of the Ministry of Shipping, later part of the Ministry of War Transport. The most significant battle that involved the merchant navy was the Battle of the Atlantic, during which the merchant fleet, with its naval escorts, struggled to bring food, fuel, equipment and raw materials from America and elsewhere across the Atlantic, while Germany mobilized U-boats, battleships, aircraft and mines against them in an attempt to sever Britain's supply lines.
Ancestry UK

Merchant seamen crewed the ships of the British Merchant Navy which kept the United Kingdom supplied with raw materials, arms, ammunition, fuel, food and all of the necessities of a nation at war throughout World War II - literally enabling the country to defend itself.
Wiki

The RN sails at the RFA's behest which are manned by the MN.