Why was the attack at Pearl Harbor not considered a complete success?

Answer 1

It was a tactical victory for the Japanese Navy, because they had destroyed much of the UN Navy's battleships; with a low loss rate. It was a strategic victory for the US Navy, because the USN would now rely on AIRCRAFT CARRIERS, since the battleships were out of commission. If the USN had used battleships against the Imperial navy's carriers, the USN would have lost the naval war to Japan. US entry into the war is also considered a strategic defeat for Japan,which is true, but this is a "catch all phrase" for lazy historians to use...as the US may well have entered WW2 for other reasons, as it did in WW1 (for unrestricted submarine warfare reasons). German submarines and US Navy surface vessels had been trading shots well before the Pearl Harbor attack; therefore it was only a matter of time before someone declared war (again, as happened in WW1). Therefore, the real strategic defeat for Japan was the US Navy's concentration on airpower (carriers) instead of the obsolete battleships, which they certainly would have used, if they had not been sunk!

Answer 2

The Japanese goal was to do enough damage to the US Pacific Fleet that it would be powerless to interfere with the Japanese as they completed their conquests and consolidated their hold on their gains. Admiral Yamamoto, the driving force behind the decision to make the attack, hoped for six months, and this was about what the Japanese gained. So in that respect the Japanese accomplished what they hoped to do. The Japanese knew going in that any ships sunk in the shallow waters of Pearl Harbor could probably be raised and refloated, and indeed all but two of the American ships eventually were.

The Japanese had no way of knowing for certain which, if indeed, any, of the ships of the US fleet would be in Pearl Harbor when their attack arrived. The Japanese hoped to find American aircraft carriers in the Harbor, but did not. The US had only three aircraft carriers in the Pacific, and only another three in the Atlantic. The Japanese had more carriers than the US and all of theirs were in the Pacific. One of the US carriers was undergoing extensive refitting on the West Coast of the US and would be unavailable for months, leaving only two ready to fight. If the Japanese had been lucky enough to catch either of these in Pearl harbor, or both, the course of the war would have been drastically altered. These carriers were the ships that allowed the US Navy to turn back the Japanese in May 1942 at the Coral Sea, and the ships which made possible the crushing American victory at Midway in June of 1942, which was the turning point of the Pacific War. If either or both of the American carriers were lost at Pearl Harbor those battles could not have had the results they did, and the ultimate result was that it probably would have taken at least another year or two to finally defeat Japan. The failure to find the American carriers in Pearl Harbor is probably the main blemish on what was a bold, daring and flawlessly executed plan by the Japanese.

The Japanese goal was to damage the US Fleet, and not the port facilities at Pearl Harbor. (They also knocked out American aviation in the first minutes, so they could do their business without interference). Had the Japanese paid more attention to trying to damage the naval assets in Pearl Harbor, the Japanese might have reaped much greater benefit from the attack. One bomb into the doors of the drydock would have made repairing battle-damaged ships impossible short of the West Coast. No damage at all was done to the US submarine base within Pearl Harbor. In the war the Japanese started that morning US submarine sailors, who made up 1% of the US Navy, sank 55% of all Japanese ships sunk. Perhaps most crucial of all, if the Japanese had done heavy damage to the fuel farm, the Navy would not have been able to continue to use Pearl Harbor as its fleet base, and would have had to withdraw the Fleet back to the West Coast of the US. But these high-value targets were not a part of the Japanese plan, and were not considered when selecting targets.