What was a Japanese submarine doing at Pearl Harbour?

 Pearl Harbour

War in the Pacific

While December 7th, 1941 will be recalled as "The day of Infamy," the deaths at Pearl Harbour were not the first deaths in the War in the Pacific.

Three days before the attack, a Naval Lieutenant went missing during a walk around the hills, the previous week, on his return to base, he had reported to the medical corps with a dislocated shoulder. Did he come across a Japanese watching station?

The first shots fired in the war in the Pacific were from a US vessel which sank a submarine of the IJN, Imperial Japanese Navy, the question we have to ask is what was a Japanese submarine doing at periscope depth near a US naval base, when they were not "officially" at war?

Also, two civillian aeroplanes were shot down minutes before the attack began, so they could not relay the information of the incoming raids.

At the time of the attack, there was an argument in the IJN, as to should a third wave be sent to attack. The officer in charge of the aircraft was in favor of the third wave, but General Yamamoto, who had been in the United States of America before the war, said the fuel used in the third raid should be kept to fuel the air defence on the return to Japan. Yamamoto realised the third wave would be blinded by the smoke, flames, and thick oil blown into the air, so the pilots would be bombing blind.

I did question Japanese intelligence reports for several years, how could they have NOT known the carriers were on exercise, and not in the harbour?

When the intel was sent, they ships were probably in the docks, but by the time the IJN got to Pearl, they ships had left on exercise. You have the issue of the intel being sent to Japan before being resent to the navy, would it have changed plans? I doubt it, Japan was intent on a war with the USA, their intent was not to attack the USA, but to stop the USA from supporting the British forces in the Pacific as they expanded.