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Mark Weston -> RE: Jap ASW forces (2/22/2010 2:48:10 AM)
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quote:
ORIGINAL: Bullwinkle58
From context, it appears that your sources implicitly assume a more ETO-centric definition of "convoying." Formations with 15 or more merchants were small in that theater, but pretty large in Japan's context. My main objection in this thread when posters claim "Japan didn't convoy in 1942" is the assumption that Allied attacks were then risk-free, or, said another way, that there were no ASW assets present and merchants were waddling ducks. I would prefer the issue to be framed that way, rather than to, as some have done here, hide behind a "no convoy" argument. ASW assets were demonstrably present in Japanese formations in 1942. How do I know this? Because ASW assets were sunk by USN submarines in 1942.
The question then becomes, how many or what ratio of Japanese formations were escort-free in 1942? IOW, what percentage of formations should be considered in any debate over Japanese ASW effectiveness? As you suggest, those figures are difficult to procure. But those are more appropriate figures to consider than simply claiming that Japan did not convoy its merchants.
That said, I also must at least address the also implicit assumption here that convoyed (true ETO-style convoyed) ships were somehow safer than merchants in small formations with fewer ASW assets, but a higher ASW-to-merchant ratio. Convoy theory so far as I've been taught and read was not instituted to support merchants' needs. Rather, it was to leverage too-small ASW asset inventories, giving each merchant at least some protection, protection not available if more numerous but smaller and more frequent formations had been employed. Even the Allies' ETO postures in 1944-1945 did not provide sufficient ASW assets so as to allow daily departures of, say, 10-merchant formations from North America. And they were sailing to only several, high-visibility continental ports with superior stevedoring services. As I said in another post, the Japanese problem was orders of magnitude more difficult vis a vis raw material and finished goods consolidation and subsequent re-distribution. The Japanese used small (3-5 merchant, 2-3 escort) formations in 1942-1944 because they had to, driven by geographical realities.
But was attacking one of these formations safer or easier for Allied submarines than would be attacking a 75-merchant, 12-15 escort formation? A different question. More is not necessarily better. Not only quesitons of ASW coordination, but also sheer miles of open ocean to consider. An escort 10-12 miles away on the other side of the convoy might be "in" the convoy, but was usually worthless in prosecution of an attacker on the opposite side. The sub was either dead, or gone, by the time it could engage. In a 6-9 vessel formation, the escorts were closer and each could be counted on to engage, at least from the sub's POV and risk assessment.
I believe that only after dimensional questions such as these are considered (and I have no illusions that the game code fully considers them, nor do I expect it to), that one should then consider the internal, organic ASW functioning of each ASW asset in turn.
As I mentioned before, the purpose of large-scale convoys isn't just to increase escort strength for each convoy, it's a protective measure in and of itself. One fewer "unit" at sea is one fewer interception opportunity for the submarines. And generally speaking a submarine interception means a single attack followed by the need to break contact, reload, and re-intercept the next day (if possible).
Bigger was better and decidedly so; at least based on analysis of the Atlantic experience. Average ship losses per submarine attack were the same whatever the convoy size given equal sized escorts. Or in other words the bigger the convoy, the smaller the risk to each individual cargo or ship. Increased escort size also increased convoy protection in a more-or-less linear way; the more escorts, the fewer sinkings. If there was a point of diminishing returns the allies didn't have enough escorts to ever hit it. Another calculation - taking into account both increased safety from convoy size and increased escorts made available by consolidating convoys - estimated that each ship in a 90-ship convoy was ten times safer than each ship in a 30-ship convoy.
And I really don't think Japan's shipping needs were fundamentally different to Britain's. It's not as if everything ever needed in Britain was conveniently available on the docks at Halifax. The Atlantic convoys travelled between two or three major ports on each side. Shipping and cargoes were consolidated at these ports via smaller local coastal convoys and the occasional independent sailing. Coordinating and consolidating feeder convoys from around the DEI might seem difficult and complex, but no more so than from a couple of dozen ports in North and South America. Whatever the geographical specifics, there's no reason the basic model couldn't have worked for the Japanese had they been willing to make the effort.
I've read far far more about the ETO than the PTO, but my impression is that the Japanese simply suffered the same failure of decision-making as the British admiralty in WWI. The crucial difference being that when they recognised reality they didn't have the resources to recover the situation. IMO they also had far less excuse, given that history was offering such recent examples to learn from.
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