If you look at the history of the WW2 Pacific theatre, you would notice an apparent lack of Imperial Japanese Navy activity between Guadalcanal and Philippine Sea. And even these two battles were reactive in nature (in reaction to US moves). The last proactive Japanese operations were in fact Midway and Aleutians in June 1942. Therefore, for more than a year IJN practically did next to nothing, although they still had plenty of powerful warships. What would be the reason for that ?

So far I have heard two explanations: One is that the Japanese waited for a decisive battle (Philippine Sea was supposed to be that), and conserved their strength for that. The obvious flaw of this strategy would be the US's industrial capacity, i.e. the USN fleet was growing much more rapidly in the same period. The other reason would be the lack of fuel. Apparently the Japanese were in such a bad fuel situation that they didn't have much choice than to sit and wait for the aforementioned decisive battle. Fuel explanation seems flawed, because IJN had high operational tempo in 1942, even in early 1943 but then it all stopped. Also, even in 1943 and 1944 they were moving ships between bases in Rabaul, Singapore and Japan proper (which did use lots of fuel). I don't deny fuel shortages, but they do not look so severe in this period to justify complete lack of action.

Considering the vastness of the ocean, and inability of the USN to be everywhere, neither of these two theories explains why the Japanese did not mount some smaller-scale hit-and-run raids against less defended targets to keep the Allies off balance, involving perhaps forces consisting of one smaller carrier like Zuihō, a few heavy cruisers or fast battle-cruisers and accompanying destroyers. This would not have risked the heaviest major units of IJN, but would have given the Japanese some sort of initiative in the war.

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    Can you clarify why you dismiss the lack of fuel as explanatory? I believe that is the conventional answer, and it seems quite intuitively reasonable that lacking fuel for operations also prevents launching hit and run raids as a useful scale, especially considering the vastness of the ocean.
    – Semaphore
    Nov 25 at 11:33
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    First of all, they were not completely inactive (Operation I-GO) for example, second, they got Yamamoto killed by US Airforce in april '43, which may have caused a kind of paralysis in their high command.
    – Dan M
    Nov 25 at 15:06
  • You're second paragraph is a non-starter: Just because the USN cannot be everywhere does NOT imply that the IJN knew where the USN was, with enough lead time to plan and launch operations. Unsuccessful small raids is a fast road to complete defeat by a thousand cuts; while conserving fuel for one last grand battle seems both attractive to Japanese philosophy and avoids the certainty of an early defeat. Nov 25 at 15:52
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    Fuel wasnt a big issue in 43, nothing like it would be in 44 and on.
    – ed.hank
    Nov 25 at 16:25
  • @Semaphore Mainly because IJN had high operational tempo in 1942 and even early 1943. Even after that, IJN ships traveled regularly between various bases in Japan, Rabaul , Singapore etc ... Therefore, I don't think they suddenly lost all fuel. That does not mean there were no shortages, but they were not so severe.
    – rs.29
    Nov 25 at 19:53

Short answer:

IJN was not able in 1943 to find the correct opportunity for the decisive battle. So IJN denied any big involvement of her ships. This was a fantastic strategic mistake.

Long answer:

After the loss of Guadalcanl, Japanese strategy focused on defending the Solomons againt US attacks, with land-based air power. This was a fail. Both USN and IJN at that time did not involve big ships because of lack of opporunities and heavy, very heavy losses in 1942.

Later in 1943, the IJN saw her bases in Center Pacific isolated by carrier forces attacks, that destroyed air power on its bases: IJN tried only once to react and missed the US forces. Anyway this was not the sort of decisive battles IJN looked for: Japan strategy before the war was to fight an ennemy force that had made a long path with much attrition.

Later on, IJN tried to reinforce Rabaul: but she faced opposition in the forms of air raids on Rabaul: the inability to oppose to those air raids forced her to put back her ships.

So, overall, IJN could not find:

  • Opportunities according to her criteria in the Center Pacific
  • Good ways to defend the Solomons

Carrier groups were pretty much exhausted on both sides after Santa Cruz in October 1942. 1943 was used to regroup.

The Japanese had few carriers and fewer pilots. The USN had almost no carriers.

In the sense of what you're asking it wouldn't have been obvious, given the fog of war, to pursue offensive or diversion actions in 1943, the IJN just didn't have the oomph left in it. Now you can say "they should have done something", but equivalently many of us could now also say: "they should have surrendered".

Although the Battle of Santa Cruz was a tactical victory for the Japanese in terms of ships sunk, it came at a high cost for their naval forces, as Jun'yō was the only active aircraft carrier left to challenge Enterprise or Henderson Field for the remainder of the Guadalcanal campaign.[81] Zuikaku, despite being undamaged and having recovered the aircraft from the two damaged carriers, returned to home islands via Truk for training and aircraft ferrying duties, returning to the South Pacific only in February 1943 to cover the evacuation of Japanese ground forces from Guadalcanal.[82] Both damaged carriers were forced to return to Japan for extensive repairs and refitting. After repair, Zuihō returned to Truk in late January 1943. Shōkaku was under repair until March 1943 and did not return to the front until July 1943, when she was reunited with Zuikaku at Truk.[83]

The most significant losses for the Japanese Navy were in aircrew. The U.S. lost 81 of the 175 aircraft that were available at the start of the battle; of these, 33 were fighters, 28 were dive-bombers, and 20 were torpedo bombers. Only 26 pilots and aircrew members were lost, though.[84] The Japanese fared much worse, especially in airmen; in addition to losing 99 aircraft of the 203 involved in the battle, they lost 148 pilots and aircrew members, including two dive bomber group leaders, three torpedo squadron leaders, and eighteen other section or flight leaders.[85] The most notable casualties were the commanders of the first two strikes – Murata and Seki. Forty-nine percent of the Japanese torpedo bomber aircrews involved in the battle were killed, along with 39% of the dive bomber crews and 20% of the fighter pilots.[86] The Japanese lost more aircrew at Santa Cruz than they had lost in each of the three previous carrier battles at Coral Sea (90), Midway (110), and Eastern Solomons (61). By the end of the Santa Cruz battle, at least 409 of the 765 elite Japanese carrier aviators who had participated in the attack on Pearl Harbor were dead.[87] Having lost so many of its veteran carrier aircrew, and with no quick way to replace them—because of an institutionalized limited capacity in its naval aircrew training programs and an absence of trained reserves—the undamaged Zuikaku and Jun'yō were also forced to return to Japan because of the scarcity of trained aircrew to man their air groups. Although the Japanese carriers returned to Truk by the summer of 1943, they played no further offensive role in the Solomon Islands campaign.[78][88]

The IJN wasn't very clever with high tempo pilot training and replacements and their return in 1944 @ Philippine Sea was perhaps premature:

The aerial part of the battle was nicknamed the Great Marianas Turkey Shoot by American aviators

  • Having lost experienced pilots (but still having some carriers and planes), logical option would be to "bloody " replacements in some easier operation, like Japanese have done prior in China. Not to wait and throw them in jaws of USN in decisive battle.
    – rs.29
    Nov 28 at 23:42

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