What would it have taken to change the start of the Pacific War?

Great Debates
1

On December 7th, 1941 Japanese planes caught the American fleet asleep and her planes unguarded in Hawaii, and preceded to execute a well-planned and daring attack on numerous locations throughout the Pacific. Not only the US, but the British and Dutch were caught hopelessly unprepared, and Japanese followup allow it to seize a large patch of territory, which took several years of bloody fighting to retake.

How much warning would it have taken to significantly changed the outcome of the initial stages of the war? Had a US sub spotted the Japanese fleet the evening before made a difference? Would it have made things worse or better?

If you go back in time far enough, it seems that there would have to be a point in which the Allies could have improved things enough to prevent the too easy stroll for the Japanese. Had the Allies been aware of Japanese intentions in January of 1941, what could they have done differently? Would that be sufficient to at least prevent the one-sided grab of land? Would that have made any difference in the war?

So there are three parts to the question.

  1. What type of warning, information, etc., would be required. e.g. radio signal intercepts? Battle plans?

  2. How much prior notice would be required in order to make a difference.

  3. What are the goal posts for being a significant difference?

I have my thoughts, which I’ll toss out as well.

2

The “Allies” were aware of the invasion fleets headed for Malaya.

If the Kido Butai had been sighted, and it’s position and course were relayed to the rest of the world, I think it would have aborted the attack. There was much debate amongst the Japanese Admirals about launching the attack in the first place. Even with surprise, the Japanese (due to “games” they played out at HQ) were afraid they might lose some of their carriers. Against an alerted Hawaii, who knows how it (the battle) would have developed.

But the attacks and invasions on the Philippines, Guam, Wake, and Malaya would still have gone forward. Those attacks were not dependent on surprise, but speed and air superiority over the targets.

3

I think the allies were well aware of the Japanese intentions in January of 1941. We just weren’t aware of when and where they would do something about it.

Some of the damage at Pearl Harbor could have been mitigated if the allies had known the attack was coming a day or two ahead. The rest of the attacks in the Pacific weren’t a huge surprise in that sense. They went on in a kind of slow motion horror for months as the allies learned just how prepared and aggressive the Japanese were and how unprepared they (we) were.

To have stopped the invasion in the Philippines, for example, we would have needed to have mobilized and and reinforced the area long before Dec 7th. That might have stopped Japan or it might have made them move up their timetable. As it was, a lot of armies were just starting to mobilize and a lot of the troops that were combat ready had been sent to the European theater.

4

If the Japanese had any appreciation of all the oil to be had in Siberia, they could have ignored the casus belli of the US oil embargo, and not risked the exposed supply lines to the Dutch Indonesian oil. They could have taken all the oil they needed off Stalin while he was fighting the Nazis (and perhaps changed the outcome of Barbarossa by tying up his Siberian troops). They could have taken Stalin’s gold, too, at Kolyma, with the Kempeitai taking over the Gulags from the NKVD.

But the Soviets had beaten the Japanese in Mongolia in 1939, so they looked elsewhere. And Japan’s army and navy were such political rivals that any war would have to be split between the glory-hogs in each service branch.

Stupid? How about the Germans, diverting from Moscow so they could take the oil in the Caucasus, not knowing that they were sitting on an ocean of the stuff in Libya.

5

The allies were very much aware of the increasing militarization of Japan for decades. And in January 1941 the British and Americans held their first combined staff meeting, for the explicit purpose of planning for an expected Japanese attack. So while some of the details were a surprise, as was the effectiveness the Japanese military. The attacks mostly weren’t.

By mid ‘41 men, planes, guns, and other equipment was being poured into the Philippines as quickly as the US could get them there. Unfortunately McArthur’s plan didn’t anticipate an attack until around March when the “cold” season came to an end. With another 20,000 US troops and an additional 3 months training for the Filipino troops Luzon would have been a vastly tougher nut to crack. Likewise the British were reenforcing Singapore/Malaysia as quickly as possible… given that they were already fighting another war. In fact several thousand men arrived in Singapore just in time to surrender, without ever having fired their rifles. A few days’ or weeks’ notice simply wouldn’t change the basic problems of not enough men or equipment in the theater.

Add on top of this the fact that “Plan Dog” had by then been widely accepted and agreed to by the American and British military, which agreed to a primarily defensive posture against Japan. So even prior to US involvement the basic agreement was to beat on Germany first and simply hold against the Japanese. Which meant that the US was transferring Naval units from the Pacific to the Atlantic in 1941. And of course most Army units were already pre-allocated to the European theater.

They only way the Allies could have slowed the Japanese, would have been to prioritize the Pacific. And that would have had bad effects in North Africa. Stripping out a few divisions would have prevented Crusader and may have given Rommel the opportunity to actually seize Egypt to Suez. Not an easy choice.

On a individual operations level, the Allies could have done better. But not by much. With a few hours notice, Pearl could have been defended far better. Simply getting ammo out of storage and next to the AA batteries, having the army planes ready to fly, recalling the sailors from leave, and having the internal water tight doors closed on the ships would have all vastly reduced US losses and increased Japanese losses. A day’s notice would actually probably been terrible for the US. The fleet would have sortied, and without air cover would have been wiped out in deep water. Probably twice as many men lost and the ships couldn’t have been repaired like most of them eventually were.

Give McArthur a week’s notice, and a better idea what he was facing, and Bataan could have been made a lot less horrific. But the US was always going to be defeated there by the Japanese. The US ran out of time for supplying the islands before they could defend them. And the re-supply lines hadn’t been built up yet. So the US had no way to relieve McArthur.

For the British? Hong Kong was a lost cause. Malaya and Singapore probably could have been held against the initial attack. The British did outnumber the Japanese in that area. But they were green and the Japanese had advantages of internal lines, vastly more aircraft and veteran troops.

The Dutch were in a hopeless situation. They had about 35,000 men and about as many reserves. But aside from a solid core they were always under-trained and under-equipped. And 3 light cruisers and 7 destroyers were never going to be anything more than a speed bump to the Japanese. The only Dutch hope lay with the US or the British.

6

Recent very similar thread.

7

This is specifically the thread I was thinking of when I created this one.

However, that thread is based on the US destroying the Japanese fleet at Pearl Harbor, but doesn’t say how. This thread is more about what could be required prior to the shooting actually beginning and how that would have affected the outcome.