The Hunted, Overview of The Japanese Merchant Fleet

The Japanese merchant ship Burma Maru, sunk by the US submarine USS Swordfish during World War II on June 12, 1942. Credit: The Australian War Memorial 

The names of many Japanese merchant vessels in WWII end in maru (丸). The earliest recorded instance of a ship with this name ending is the Bandou-maru (坂東丸) recorded in a document of the Niwaji (仁和寺) temple in 1187, during the Heian era (794-1185).

Multiple origins of maru have been suggested by contemporary scholars. One theory is its origin it comes from the name ending maro (麿) used for objects of affection. Other theories are, logs, maruta (丸太), used to build the early vessels or from the round, tub-like shape of early vessels. Others are or the name of a Chinese figure, Hakudoumaru (白童丸), said to have descended from heaven and taught shipbuilding, name of wholesalers, once known as monmaru (問丸), the maru of whose name was then transferred to the boats, or from the castle-like nature of the ships.

U.S. map of Japanese shipbuilding centers, 4 June 1945

The Imperial Japanese Navy employed number of merchant ships during the war. The merchant fleet included general cargo ships, passenger/troop ships, bulk carriers, and tankers for oil and natural gas. Merchant ships varied in size, from 20 ft long to as big as 1,361 ft long.

As the war progressed the IJN converted numerous civilian ships, as well as captured vessels from the British and the American fleets. It is worth noting that Axis ships (French, Italian, German, Dutch, etc.) were in IJN service as well. Most served as just cargo or transport ships, but many of them were remodeled as amphibious ships, seaplane tenders and escort carriers as well.During the war, the IJN provided little convoy support to its merchant fleet. Therefore, the loses on cargo vessels were high by the end of the War. Which was the opposite of the USN logistics of Naval warfare in WWII. Compared the IJN loss of merchant ships during the war which was 2,346, the USN lost about half the number, 1,182 ships where it protected and escorted its merchant transporting vessels.