From: Bexhill-on-Sea, E Sussex
I came accross this little item. It might be of interest.
The Shipping War
The War in the Pacific depended, like any other, on supply. Being an ocean war, the supplies, quite naturally, had to go by ship. At the beginning of the war, the shipping available to both Japan and the United States was, surprisingly enough, quite equal. Japan had some 5.98 million tons of shipping while the USAhad some 6.7 million tons. The crunch, however, came when one compared the shipbuilding capabilities of the two nations. Japan, an island nation, had to import to survive. Japan had few natural resources. And Japan could only build some 600,000 tons of new shipping each year. America could build over ten times that amount, and was doing so by 1943. Before the war began, the United States had already started on a shipbuilding campaign which was to produce 10.8 million tons during 1942-43. This was increased once America entered the war. Of course, the majority of American shipping was to be engaged in getting material to Europe and fighting its way through Nazi U-Boats in the North Atlantic. The Germans lost the Shipping War in the Atlantic, but only after sinking 23.3 million tons of shipping. On the other hand, the Japanese sank or seized only a million tons of shipping during 1942 (and not much after that). Much of this, of course, was not American shipping, but these ships were lost to the Allied cause. The Allies eventually built far more (some 19 million tons more) shipping than was sunk. The Japanese weren't so fortunate. From the very beginning the Japanese realized that they would have to carefully ration their available shipping. They were all too correct in this estimation. In fact, from the very beginning (despite the 400,000 tons of enemy shipping they seized initially) the Japanese merchant marine declined. Slowly at first (a net loss of less than 200,000 tons in 1942), but the effects of the American "U-Boat" campaign soon took hold. By mid-1943 the net loss (from the 1941 tonnage) was 440,000 tons. After that one crisis followed another as the Japanese vainly tried to do more with less shipping. What DO you do with shipping ? You carry troops. An American infantry division required from 70,000 to 100,000 tons of shipping. Once carried across the Pacific it required another 15,000 tons a month to maintain it. The "lift" tonnage fell as the war went on due to increased experience and expertise in putting men and equipment aboard ships. Other units required more tonnage to "lift". Overall, the 518,000 men carried to the Pacific in the first eighteen months of the war required some 3.6 million tons of shipping. Once there, they required some 500,000 tons of shipping a month for maintenance. In the first eighteen months of the war, the United States Army moved some 1.6 million men and some 23 million tons of material overseas (only 6 million tons went to the Pacific). The US Navy tied up some 600,000 tons of shipping, mostly for maintaining the fleet. By mid-1943 some 200,000 naval personnel (including Marines) were in the Pacific. Over half of the US fleet was concentrated in the Pacific. This increased after mid-1943 with the neutralization of the German U-Boat offensive in the Atlantic. This German defeat was but another nail in Japan's coffin.
At the beginning of the war, Japan calculated that 3 million tons would be needed to maintain their economy. This left some 3 million for the military to use in their offensive. But to support an offensive in the Pacific would require some 2.1 million tons for the Army alone, plus 1.8 million tons needed by the Navy. Of course, the shipping allocated for the Army would gradually decrease as the Army completed its troop movements. Initially the Japanese Army had to move some ten divisions (or their equivalent) by sea. This took up some 700,000 tons of shipping. Also to be moved were engineer, aircraft support and base maintenance units. Finally, all of these units had to be supplied. Not as lavishly as American units, but you couldn't grow ammunition and equipment locally. By the Spring of 1942, the Japanese had some 250,000 land-based troops in the central and south Pacific. These required nearly 200,000 tons of shipping a month to supply. In addition, every time a unit was to be moved, more shipping was tied up. The Japanese planned to reduce army shipping to one million tons by August of 1942. Navy shipping was expected to remain constant at 1.8 million tons. This would leave 3.2 million tons for the civilian economy, which produced all that the armed forces needed to wage war.
In early August 1942 American forces went over to the offensive, seizing Guadalcanal Island. The Army, in the course of its attempts to retake the island, took away from the homeland shipping fleet some 400,00 tons of shipping. But this was quickly stopped, for since the war began, Japan had not been able to muster the necessary three million tons of shipping needed for her economy. At the outbreak of the war the Army had 2.15 million tons, the Navy 1.55 million and the economy 1.71 million tons. By August 1942 this had changed to Army, 1.27 million tons; Navy, 1.5 million; and the economy 2.76 million tons. by January 1943, at the peak of the Army's build-up to retake the "Southern Areas" held by the Americans, the Army controlled 1.41 million tons of shipping, the Navy 1.46 million and the economy 2.34 million tons. American attacks on Japanese shipping increased throughout 1943 (the Japanese refused to adopt a convoy policy until too late, and then American subs had adopted the "wolf pack" technique). The Japanese managed to build 3.2 million tons of shipping during the war, but Allied air and naval units managed to sink some 7.5 million tons, all but a million tons of it after mid-1943. All things considered, Japan never had enough shipping to meet the demands of a naval war in the Pacific. The United States was not much better off for the first eighteen months of the war. At the beginning of the war the Army had 778,000 tons of shipping available to it. By the end of 1942 this had risen to 3.9 million tons and by mid-1943 approached 5 million tons. But after the Spring of 1942 the bulk of available shipping went to the Atlantic. Shipping in the Pacific reached a peak in May 1942 with 2 million tons in use. By the end of the year there was but 1.14 million tons available 1.7 million tons and this amount continued to grow until the war's end. Even though the United States committed itself from the beginning to the defeat of Germany first, additional tonnage had to go to the Pacific in order to move ground troops and aircraft units into what, for all practical purposes, was a vacuum. Once this had been accomplished (and particularly after Midway crippled the Japanese carrier force) the Pacific had to get along on what could be spared from the Battle for the Atlantic. This meant that much of the American material superiority could not be brought to bear on Japan immediately. For example, in 1942 Japan produced 12,100 combat aircraft, the USAproduced 30.800. But only B-17 heavy bombers could be flown out to Pacific bases, all others had to come by ship, as well as the base equipment and personnel for all aircraft. What about Japan's submarine Fleet?It was, initially, the equal of America's. It was crippled by a doctrine which prohibited the wasting of torpedoes on merchant ships. Japanese submarines were expected to go after combat ships, and nothing else. The Japanese held to this doctrine throughout the war. What if they had adopted the more logical approach, and gone after US merchant ships? This would have probably had a two-fold effect. First, it would have inhibited the US fleet in the Pacific. Destroyers and other light fleet units would be taken away for escort duty to a much greater extent than was actually the case. The second effect would have been felt in the Atlantic. Shipping lost in the Pacific would have to be made up, it was at the bare survival level as it was. This would have probably meant that the American invasion of North Africa in late 1942 would have been put off, or at least seriously curtailed. Much of the same effect would have been evident had the Japanese not been stopped at Midway. But the Japanese could have hurt the Allied cause tremendously simply by changing their submarine doctrine. They didn't, and the Pacific War ended that much sooner. Decided, to a large extent, by hundreds of lightly armed and rather unmilitary looking merchant ships.
A footnote on Japanese and American Merchant Ships
As the war progressed the USA gained not only a quantitative edge over the Japanese in military equipment, but a qualitative one also. This was also evident in the wartime merchant shipping built by both nations. During 1941 America began building a new class of merchant ships, the Type EC2-S-C1 (or "liberty" ship). During the course of the war over 2500 of these vessels were produced. The basic version (there were numerous sub-types for special applications) was 441 feet long and had a lift-capacity of over 14,000 tons. Vessels of this type alone amounted to over 30 million tons of shipping. The EC2-S-CS1cruised at about 12 knots and had a crew of 45 (plus a gun crew of 36). The Japanese never had anything like it. At the outbreak of the war the Japan ee merchant fleet had only 19 ships with a lifting capacity of over 10,000 tons. The ships they built during the war averaged between 2,000 and 3,000 tons each. Their performance was also below the American standard. Their cruising speed, for example, was often 30 to 50% less than that of American merchant ships. This was not particularly crucial during normal operations, but when these ships were used to transport troops in the combat zone their slow speed became decisive. Even during normal shipping operations this slow speed had its effect. For all their shipping tonnage, the average "time" from Pacific areas to the Japanese homeland was greater distances to the US West Coast. The main reason for the slowness of Japanese shipping was the "bottleneck" in their shipbuilding industry caused by an inadequate engine industry. Japan could have produced twice as many merchant ships had they a larger marine engineering capacity. They spread this capacity as thin as possible, thus producing smaller, slower ships. Both Japan and the United States produced special "fast transports."Both nations usually used converted destroyers. In addition the United States was able to produce a special line of "fast transports" built specifically for the task. The United States was also far ahead in its ability to produce amphibious shipping. Even in 1942 the United States was able to unload merchant ships in the combat zone in one third to one half the time it took the Japanese.
Were did I find it? In this games predecessor's manual - PACWAR