Two questions about WWII - south Pacific

First, how effective were the coast watchers, really? I know the arrangement with the volunteers increased the Allies’ observation capability by nearly a hundred fold but did they really figure in a major engagement (observation and reporting that is)?

Second, why did Japanese ships attacking the American landings at Guadalcanal have to pass through the space between two lines of islands in the Solomons, known as “the slot?”

These were Japanese controlled islands. They had their own observers and patrols throughout the area. They could tell if any American forces were coming into the area and respond to them. Made for much safer traveling, especially for the slower moving transports. Also their ships were harder to spot among the islands. So the US basically kept their naval forces out of the area and just did occasional air patrols.

I have read Neptune’s Inferno: The U.S. Navy at Guadalcanal by Hornfischer. Good read if you’re interested in this bit of history. From my memory:

  1. During the Guadalcanal campaign it appears that the American coastal watchers in the area were somewhat effective at spotting incoming enemy ships. Unfortunately there appears to have been several breakdowns in communicating information from them to Admirals out with their ships in the fleet. The watchers would report to some central place - it would be decoded there and filtered back out to the Admiral later but typically too late.

The Japanese did not have to pass through the slot - and I don’t think their ships always did during their many runs in and out of the area. However - it was a convenient quick route and they needed speed. The Japanese owned the sea at night - the Americans the day. This is solely because the Americans had the airbase but could not fly their planes at night. The Japanese had to wait until cover of darkness, get in and do whatever they were going to do (usually unload soldiers/cargo but occasionally attempt to bombard the American airfield) and then get far enough away from the area that the American planes couldn’t take off in the morning and find them.

Thanks gents!

Walter Lord’s “Lonely Vigil” is a good book about the coastwatchers.

It describes instances where they gave early warning on airstrikes, allowing Allied forces to get defenders in the air and defend installations/ships.

They also were involved in the rescue of numerous downed aviators.

The Coastwatchers gave Allied forces raid warnings. The Guadalcanal campaign was pretty much a war of attrition, ultimately for both sides, and the Cactus Air Force really appreciated advance knowledge about what was headed towards Henderson Field.

Meaning no disrespect to the coastwatchers, who did indeed perform valuable services, I’ve often wondered if a certain amount of intelligence derived through cryptography (particularly the American decryption of JN-25, Japan’s navel code) was deliberately misattributed to coastwatchers in order to conceal the cryptographic success. The Allied codebreaking remained secret long after the war, so even early post-war histories would have had to account for apparent Allied foreknowledge somehow.

Generally speaking, the Coastwatchers were usually Australian, not American. They were the colonial officials and settlers who stayed behind when the Japanese came and found refuge among the natives. In fact, the Australian government set up a bureau dediacated to managing the Coastwatcher program.

The Cactus Air Force (named after Guadalcanal’s American code name “Cactus”), in addition to raid warnings from Coastwatchers, had an additional geographic advantage. The distance from the main Japanese base at Rabaul to Guadalcanal dictated that if the Japanese wanted to land plans during daylight, the air raid would have to leave around dawn, which usually put them over Henderson Field about noon. So, the Marine pilots could get ready in the early part of the morning, then head out to their planes to wait for a radio warning from Coastwachers on up the Slot for inbound Japanese bombers.

“The Slot”:

Rabual, Bougainville, and the Shortlands were the main Japanese base & staging areas (with airfields) in the Solomon Island area, and the shortest, most direct route to Guadalcanal was down “the slot”.

If the Japanese were to swing wide, and try to approach Guadalcanal from another direction, that would inevitably lengthening their time in transit, and providing that much more time for said force to be detected, and some kind of American welcoming party assembled. Additionally, in a lot of cases, the Japanese could not control the airspace over Guadalcanal, and wanted their ferrying ships out of harm’s way by daylight, after dropping off the troops and/or supplies.

I wish my Father were still alive. He was in Australia and New Guinea working on airplanes. He told me about the Coastwatchers. I would like to ask him if he knew about them during the war. Probably not.

Was that the battle where the Japanese transports were sunk, but because they were close enough to swim ashore, the navy aviators had to go back and kill the swarms of guys in the water, and they were throwing up in their face masks while doing it? Or was that a different battle?

That was the Battle of the Bismarck Sea, in March, 1943 when the Japanese were trying to run a troop convoy to New Guinea.

For a while i thought this was going to be about a shortage of dames in a backwater base area.