What were the cons of attacking Pearl Harbor?

Answer 1

There were a very large number of drawbacks and perils in the Pearl Harbor attack for Japan. So many, in fact, that the only reason the attack was made was the force of Admiral Yamamoto's personality. What Japan was after was a free hand in Asia, freedom to continue their invasion in China, and, specifically, to make their next move unmolested. Japanese aggression in China had severely strained US-Japanese relations. Then the Japanese moved into French Indochina (Vietnam) after France was overrun by Germany, adding further strain. The Japanese had now set their sights on the Dutch East Indies (Indonesia). This was a vital step in Japan's plan. The East Indies had tremendous oil reserves. Japan has no internal source of oil, and the US had embargoed oil sales to Japan in the summer of 1941. The Japanese had only eighteen months worth of oil in reserve, and the embargo made the choice plain - either give up on the dream of empire, to which Japan felt entitled, and comply with US demands to cease aggression and conquest, or come up with another source of oil. With the military in control of Japan this was no choice at all, and the Dutch East Indies were going to be invaded. This was the main operation, the one which absolutely HAD to succeed for Japan to continue with its plans.

The Japanese decision to attack Pearl Harbor was based on an assumption - that the US would go to war with Japan if Japan invaded any more countries, say, for instance, the Dutch East Indies. Whether the US would have gone to war over Japan invading a Dutch colony is far from certain. The military leaders controlling Japan did not completely understand that Franklin Roosevelt did not have the power they did, to take his nation to war whenever he might wish. The Japanese assumed that the US would go to war with them when they made their "southern" move into the Dutch East Indies, and this was the basis of the decision to attack Pearl Harbor. Yamamoto knew he could not win a long or protracted contest with the US. Yamamoto had served in the US as a Naval Attache at the Japanese Embassy, and he was a Harvard man. He knew the US had much more power than Japan. The only chance Japan had, as Yamamoto analyzed the situation, was to strike such a blow to the US fleet in the Pacific that the US would be powerless to interfere with Japan's wars of conquest for at least six months. This would allow time for Japan to complete its conquests, and the US would then face the prospect of a daunting and long effort to dislodge Japan, and might allow Japan to keep what it had won.

So that's one BIG drawback to the Japanese plan. There was no certainty whatsoever that the US would have gone to war with Japan over any Asian aggression. The only way to make certain that the US would go to war with Japan was to attack the US directly, as the Japanese did, when they attacked to disable the US Pacific Fleet in Pearl Harbor.

Many Japanese felt the Pearl Harbor plan was an unnecessary elaboration of their already complex and widespread southern plans. The attack on Hawaii would tie up the majority of Japan's carrier strength, and the Japanese expected they would lose half the carriers committed to Operation Hawaii. The Japanese had a limited number of carriers and using them in an attack on Hawaii meant they would not be available for supporting the main operation. Japanese strategy had envisioned a climactic battle with the US in the western Pacific, an all-out, do-or-die battle to determine the fate of their nation, in the event war came with the US. For this reason their ships had limited radius of operations - they lacked fuel capacity to sail to Hawaii and back without being refueled. The Japanese Navy had not practiced refueling at sea while underway, except of destroyers. Only two of the six carriers could make the round trip without refueling. Seven tankers sailed with the attack force to refuel the fleet while underway. In order to avoid detection while in transit to Hawaii the Japanese had to sail east across the North Pacific, then turn south for Hawaii, avoiding usual shipping lanes. The North Pacific weather in December in unpredictable but generally stormy, with massive seas and fog. It was far from certain that underway refueling would be possible.

The Japanese could not be certain that the US fleet would even be in Pearl Harbor when their attack arrived overhead. Japanese spies had reported that the US fleet had established a pattern of half its ships in port while the other half was at sea, with the largest number in port on the weekend. But no one could be certain that major fleet units would be in port when the attack went off. In the event, the US carriers were absent, most unfortunately for Japan.

The Japanese knew they had to have secrecy and approach undetected for the attack to succeed. At the last meeting before the fleet sortied, Yamamoto warned that the fleet might have to fight its way to the position to launch its attack.

The Japanese could not be certain that the US would not have taken the sensible precaution of surrounding the ships in Pearl Harbor with torpedo nets. The most devastating weapon in a carriers arsenal was the torpedo, launched from the largest carrier aircraft of the day, torpedo bombers. The US did not use torpedo nets in Pearl Harbor, because the Harbor is shallow, no more than forty feet deep. Torpedoes generally dived to a depth of seventy-five feet or more when dropped, so the US admirals believed aerial torpedo attack impossible within Pearl Harbor. So did the Japanese, and it took most of 1941 to train torpedo plane pilots to come in low enough to drop specially modified torpedoes which did most of the damage in the attack.

Carriers embarked torpedo bombers, dive bombers and fighters. Dive bombers dropped 500 lb bombs. These would not go through the thick deck armor of US battleships, and might cause damage on the weather deck, but nothing vital. The Japanese solved this problem by using torpedo bombers as high level bombers, which dropped specially modified one ton battleship armor-piercing shells as bombs. It was one of these which sank the USS Arizona. The high-level torpedo bombers also had to practice and develop special tactics for most of 1941 to achieve success.