Why had the Japanese not disembarked on Pearl Harbor and annihilate the base and everyone there?

They had surprise.  And you have exactly that time window to exploit that surprise.  The  real choice was to do Malaya and Singapore or to occupy Hawaii.  Anchoring the  bulk of the Japanese fleet at Pearl would have allowed the entire  island chain to be fully occupied and DEFENDED.

The USA woud have been forced to sit on the west coast and build up resources and manpower against a potential Japanese attack and invasion which is a pretty miserable strategic position.   

The Japanese would need to postpone their SE asia expansion but that was completely possible with the weight of the British Empire tied up in Europe..

Recall that Midway was the equalizer in this year.  An intact carrier fleet protecting Hawaii and also supporting pressure on Australia would be a tough challenge and would certainly have postponed offensive operations anywhere in the Pacific until after Europe was dealt with.  This is what did happen to allied forces in england.


Why had the Japanese not disembarked on Pearl Harbor and annihilate the base and everyone there
M.M. Holmes

Freelance Historical Writer

In the late 1970s-early 1980s, University of Hawaii History Professor, Emeritus John J. Stephan reviewed Imperial Navy General Staff and the Combined Fleet records, along with interviewing Combined Fleet planning officers who served prior to, and during, the Pacific War. Professor Stephan’s findings were outlined in his book “Hawaii Under the Rising Sun” (1984).

In his research, Stephan noted that during Summer 1941, plans officers in Combined Fleet had proposed that an invasion force immediately follow the bombing of Pearl Harbor. Given the intelligence they had of US defenses, the officers were convinced that an invasion of Oahu, Maui, and the Big Island would be successful. But the Navy General Staff rejected this plan, mainly because all available troopships would be needed for operations against Malaya and Singapore.

As late as November 17, 1941, two Imperial Navy intelligence officers who had masqueraded as passengers on a Japanese cruise ship, reported to the Navy General Staff in Tokyo their findings as to ship movements and defenses around Pearl Harbor. Beyond this information, the two officers requested that the General Staff consider an invasion of Oahu as a follow-on to the bombing.

Their impression was that Oahu could be successfully captured with just two infantry divisions, combined with ongoing Naval air support. While the Navy General Staff agreed that two divisions would probably be sufficient, the Staff’s concern was how to re-supply and maintain an invasion force over the vast reaches of the Pacific. The officers’ report was apparently filed away, but noted by Combined Fleet.

After the successful raids at Pearl Harbor on December 7, 1941, Admiral Yamamoto was said to be frustrated and extremely regretful that he had not pushed harder for a follow-on land invasion of Oahu, given the element of surprise and lack of resistance by US forces on Oahu. The capture of Oahu, even if only for a year or less, would have pushed back US Naval operations to the West Coast, and severely hampered their ability to challenge Japan’s intentions in the South Pacific.

Vice Admiral Tamon Yamaguchi, IJN

Yamamoto’s solution to this missed opportunity was “Eastern Operation”. The first phase was to capture Midway Island while destroying US carrier forces during the Battle of Midway. Subsequently Palmyra and Johnston Atolls were to be occupied, as well as French Frigate Shoals in the Northwest Hawaiian chain—for use as staging areas to support the invasion of Hawaii by late 1942. Western-educated Admiral Tamon Yamaguchi, Yamamoto’s heir-apparent at Combined Fleet and said to be more daring than Yamamoto, would have led “Eastern Operation” before he went down with the carrier Hiriyu at Battle of Midway.

An invasion of Hawaii would have required expanded support by the Japanese submarine fleet. It had already conducted limited operations out of French Frigate Shoals during “Operation K”, the second (attempted) bombing of Pearl Harbor in early March 1942. But even if the US had lost its carriers at Midway, it could still read over 80% of Imperial Japanese Navy communications. The US would have had enough time to build up the defensive perimeter in and around Hawaii before “Eastern Operation” could ever be implemented. Meanwhile new American carriers would launch to join the Pacific Fleet and retake the offensive.