Appendices - Hirohito's War
OIL, RAW MATERIALS, AND LOGISTICS: ‘JUST START SWINGING’
Japan’s Cargo Ship Problems: While the United States had settled on a single, low cost, mass produced prefabricated design to solve its naval transport problems, Japan’s leaders appear to have given little thought to the long term logistical issues. It was only in 1943, when Imperial HQ woke to the looming catastrophe of supply caused by the increasing tonnage lost to US submarines, that Japan turned its attention to the mass production of a large format cargo ship akin to America’s Liberty Ships.
Until 1943 Japan built traditional high spec cargo ships from a plethora of designs. As with their manufacture of warships there were too many variations and not enough focus on quantity and the development of more productive construction techniques. In 1942 and 1943 Japan built 21 B-1 Class (7,336 DWT), 44 C-1 Class (4,476 DWT), 34 D-1 Class (2,850 DWT), 19 E-1 Class (1,265 DWT), 31 F-1 Class (700 DWT) and 32 K-1 Class (6,433 DWT: Specialist ore carriers).
As the Imperial Japanese Navy grew increasingly fearful of the consequences of the mounting rate of cargo ship losses (See Appendix A: Submarines: America Draws Tight the Noose), new techniques of manufacture and assembly were developed. The A-I Class and rapidly updated A-2 Class cargo ship was a standard design authorized by a panic stricken Ministry of Communications working in conjunction with the Imperial Japanese Navy. The vessel, which had a deadweight (DWT) of 10,425 tons, was 455ft long and 58ft wide and could travel at 15 knots; the design notably differed from the Liberty in the setting of the engine room toward the back of ship to reduce the length of shaft required.
The A-2 Class (and its A-3 successor of which only one was built) was a ‘prefab’ designed ship for which new dockyards were specifically built. In its construction the A-2 Class was significantly hampered by the lack of large format gantry cranes; Japan did not have cranes that could lift a 50-ton section as was typical for the Liberty.
Nevertheless build time for the A-2 was gradually reduced from 90 days to 36 days. In operation, the A-2’s slow speed, rickety construction and unreliable engines meant that it suffered a poor reputation and was shunned by the Army and Navy who preferred higher quality pre-war designs when they were available. Many of the later A-2s were converted to tankers as US aircraft and submarines increasing focused on sinking oil tankers as a means to cut off Japan’s supply of oil. Out of the 83 A-2 Class ships launched from December 1943, no less than 55 were sunk in the remaining 20 months of the war.
In addition to the larger A-2 Class cargo ships, the Ministry of Communication focused on revamped techniques for smaller vessels E-2 Class (successor to E-1). As with the A-2 Class, new shipyards were constructed to enable rapid fabrication and assembly. In 1943 the new streamlined yards managed to launch 58 E-2 Class; improvements in productivity produced 296 E-2 ships in the following year. Noticeably, as raw material supply suffered a sharp decline, just 54 E-2s were produced. The D Class was also revamped albeit a year later with the development of a modular system for the D-2 Class; in 1944 Japan produced 54 D-Class cargo ships falling to 29 in 1945.
Although the ‘2’ series cargo ships (A-2, D-2, E-2) constructed with new modular systems produced an aggregate 1.67m DWT compared to 0.8m DWT produced by traditional fabrication techniques (Classes: A-1, B-1, C-1, D-1, E-1, F-1, K-1), it was too little too late. By comparison, at the peak of Liberty Ship production, new tonnage was 1.4m DWT in December 1943 alone. At the end of the war gross US merchantman inventory had risen to over 8.0m tons (DWT) compared to just 200,000 operational tons remaining in the Japanese commercial fleet.
If Imperial General HQ was completely unprepared to make good the losses that would be incurred in Japan’s mercantile fleet, it was equally unprepared for the protection of its existing inventory. Not only was there no convoy system to safeguard trade flows to Japan but at the outbreak of the war Japan had just four purpose built escort destroyers. It took until July 1943 for the armed services and civilian authorities to hold monthly conferences to monitor and coordinate shipping resources. Nevertheless shipping coordination was so poor that, in spite of the severe domestic shortages, many cargo ships carried ballast back to Japan. Dedicated armed forces ships, of which the Army had 519 totaling 2.16m tons and the Navy 482 ships (1.7m tons), would often refuse requests to carry goods.