In pearl harbor did they have anti aircraft guns?

Answer 1

They did, but they did not have enough of them. The US Army was responsible for defending the islands, and the fleet, when the fleet was in the harbor. The army commander at the time of the attack, his predecessor, the fleet commander and his predecessor, had all informed Washington that additional anti-aircraft guns would be needed to adequately defend the fleet in the harbor, but nothing was done.

The ships of the fleet also mounted anti-aircraft guns, but not very many. Experiences of the early months of the war caused the US Navy to add dozens of anti-aircraft guns to US vessels, particularly 20MM and 40MM automatic cannon. At the time of the attack the principal navy anti-aircraft weapons were quad-.50 caliber machine guns, 1.1 inch cannon, and the 5 inch/25 caliber naval cannon, all of which soon proved their unsuitability in this role and which were swiftly discarded.

The Army's principal anti-aircraft gun was a 90MM cannon, an excellent weapon, but sadly not yet available in quantity. It was a fairly new design.

An air raid on Pearl Harbor was not regarded as a big threat. The raid would have to made by carrier planes, and carriers had two types of bombers - dive bombers and torpedo bombers. It was thought torpedo bombers could not be used because the waters of the Harbor were too shallow. When US torpedo bombers released their torpedoes they went as deep as seventy feet before coming up and stabilizing to run at their preset depth - usually 8-10 feet. Japanese torpedoes did the same, and since the harbor was only forty feet deep at its deepest, the threat of torpedoes was discounted. The Japanese overcame these problems by fitting wooden fins to their torpedoes for greater buoyancy and by endless hours of practice at dropping them at extremely low altitude, to minimize the depth to which they would sink when dropped. They were very successful and torpedoes caused most of the damage to the US battleships in the harbor. The other type of bomber was the dive bomber, and these dropped only 500 lb bombs, which could do damage but could not cripple a capital ship. A 500 lb. bomb could not even penetrate below the armored deck of US battleships. Again the Japanese innovated, and used some torpedo bombers as "high altitude" bombers, fitted with crude bombsights. These dropped one-ton, 15 inch armor-piercing battleship shells fitted with fins. Dropped from several thousand feet these "bombs" would hit a ship traveling as fast as if they had been fired from battleship guns. It was one of these which penetrated deep into the USS Arizona and detonated the ships magazine of black powder charges used to launch the ship's observation airplane down its catapult. This magazine was adjacent to the main battery magazines, and the explosion flashed over into the forward main magazine and detonated it, destroying the ship.

So, the Japanese were able to innovate in ways the US had not anticipated when the possible effects of an air raid on the fleet in the Harbor were discounted.