Why didn't Japan invade and occupy the Hawaiian islands during the initial raid on Pearl Harbor?

by JerIrwin17

Surly this would have put them at a great advantage, seizing the one of the US'S most strategic Pacific Bases. Why not? Was it too well defended?

jschooltiger

I’ve written about this before. The short answer is that Japan didn’t have anything like the logistical capability to invade Midway, let alone the main Hawaiian islands, which are not remotely self-sufficient in food. During the planning for the Pearl Harbor attack, there was some discussion of abandoning or scuttling part of the strike fleet after the attack, as the Japanese fleet was limited in its ability to refuel while underway.

beachedwhale1945

One aspect that isn't covered in u/jschooltiger's earlier comment is the Japanese didn't have the ships available for this operation. However, to explain that I must go slightly off topic for a bit.

When Pearl Harbor is usually discussed, it is discussed in isolation, as if it was the only major move the Japanese made at that time. However, it was a small part of a much larger operation. The Japanese had decided that they needed to conquer large swaths of British, American, and Dutch territory quickly, which required a massive portion of their Navy.

For example, let's look at major combatants. Japan had nine combat carriers, ten capital ships, 18 heavy cruisers, 17 light cruisers, 67 available modern destroyers (one in repair and one on trials not counted), 34 old destroyers, 22 huge submarines, 24 large submarines (including 4 minelayers), and 11 medium submarines^(1), plus smaller combatants, auxiliaries, and training ships I won't get into. While a strict number of ships doesn't account for the capability differences, it is useful in this case to show how many ships were in each area, and the Japanese had 212 major combatants available, of which 155 were carriers and surface combatants.^(2)

The Pearl Harbor Strike Force had the six largest carriers, two capital ships, two heavy cruisers, one light cruiser, seven modern destroyers, and three huge submarines, plus two modern destroyers for the supply group. Nearby and often forgotten was the Advance Group, another 25 submarines (17 huge, 8 large). In total, 48 ships, 22.6% of those available, but a further breakdown shows only 20 surface combatants (12.9%) and 28 submarines (49%), all biased towards the most capable warships available.

That sounds large, and in some ways it is. But the other forces were very potent. In the Northern Philippines the Japanese dispatched two heavy cruisers, three light cruisers, 8 modern destroyers, and ten old destroyers to assist the invasion forces. In the Southern Philippines and Legaspi forces, there was the light carrier Ryujo, three heavy cruisers, two light cruisers, 12 modern destroyers, and one old destroyer (Shiokaze, plane guard for Ryujo). Two minelaying submarines (and several surface-ship minelayers) were also in the area blocking likely routes from the US base in Manila Bay. In total there were 44 ships in these groups, 20.8% of the total available. The old destroyer Hokaze was nearby escorting Taiyo (at the time named Kasuga Maru), an escort carrier acting as an aircraft ferry.

Off Malaya and in the Gulf of Thailand was another group of warships. The Distant Cover Force had two capital ships, two heavy cruisers, two light cruisers, ten modern destroyers, and one old destroyer (Hakaze, SAR near Cape St. Jacques). In addition, there were ten large submarines and the other two minelayers. Actually supporting the invasions of Malaya and Thailand were five heavy cruisers, one light cruiser, and 14 modern destroyers. In total that's 49 ships, 23% of those available. Hong Kong was nearby, a light cruiser and two modern destroyers.

There were also several invasion forces in the Central Pacific, Guam, Wake, bombarding Midway, etc., which I'll summarize as one unit: four heavy cruisers, three light cruisers, 3 modern destroyers, 11 old destroyers, and nine medium submarines. That's 21 ships, 10% of those available. There were also two huge submarines on scouting missions to Pago Pago and Alaska, now completed and moving towards Hawaii and California.

In total, for all offensive operations, the Japanese had deployed seven of their nine combat carriers (hereafter deployed/available), 4/10 capital ships, all heavy cruisers, 13/17 light cruisers, 58/67 modern destroyers, 24/34 old destroyers, all huge submarines, 22/24 large submarines, and 9/11 medium submarines. In total the Japanese only had 35 ships available that were NOT committed to some invasion force. Most of these (the two carriers, six battleships, two light cruisers, and eight modern destroyers) were part of a reserve force in Japan in case something went wrong, and the rest were with in overhaul or part of the local defense forces.

That's not enough surface ships to support an invasion of Hawaii, the main American naval base in the Pacific. Once you factor in ships less than a week away from the harbor the Japanese would be outnumbered by 2:1. Moreover, while that analysis isn't complete, it appears most of the Japanese transport fleet was also committed to these invasions.

Sources:

Dr. Leo Niehorster has an excellent website listing orders of battle and ship locations, and his Initial Operations Page for Japan has been invaluable. I have also been cross-referencing his data with CombinedFleet, which tracks the movements of hundreds of Japanese ships during the war.

Footnotes in a reply to this comment.

PlainTrain

Oahu would be a difficult invasion target. It had 35,000 troops in two infantry divisions and the Hawaiian Coastal Artillery Command. There are only two practicable invasion beaches--the North Coast, famous for its high surf, especially in Winter, and the area around Honolulu where most of the coastal defenses were. Despite the success of the Pearl Harbor attack, the Army still had a substantial bomber force present, and the Navy had its aircraft carrier, cruiser, destroyer, and submarine force largely unscathed. The surviving battleships could also contribute in an emergency.

The closest Japanese base to Oahu was over 2000 miles away. It took every fast tanker in the Japanese inventory to get eight capital ships within 200 miles of Pearl Harbor, and without any ability to replenish stores and ammo underway, the six carriers had pretty much shot their bolt. The Japanese didn't have the logistical capability to get a force to Oahu and keep it there long enough to seize it.

"The Reinforcement of Oahu", GUARDING THE UNITED STATES AND ITS OUTPOSTS