Richard Woodman, aside from being an excellent nautical fiction novelist, is a naval historian of some note. His Arctic Convoys, was highly regarded and The Real Cruel Sea is a readable, thorough, celebration of the unsung heroes of the Battle for the Atlantic. As he notes, without the constant flow of materiel and supplies, the invasion of Europe by the allies could never have occurred. It was the flow of old tramp steamers and Liberty ships that kept things moving.
These ships were manned by theoretical non-combatants who had no special status and often lacked even the primitive comforts of the regular armed services. If their ship was sunk they went "off-pay." "Exposure in a lifeboat or on a raft was an unpaid excursion."
The Royal Navy regulars often failed to appreciate the hardships of their merchant mariner cousins and often cast a jaundiced eye at the oil-soaked, inebriated survivors of a torpedoed ship, not understanding that raids on the ships stores of alcohol were often the last comfort for a sailor facing an indeterminate time in a lifeboat or in the sea, if they were saved at all. They died in greater proportion to their naval equivalent and, ironically, perhaps, suffered the most in the postwar depression that Britain faced as late as 1949.
This is a detailed, substantial, and very interesting book.