In what way was the attack on Pearl Harbor an intelligence failure? To me, the term intelligence failure seems to imply that the US could've known that the Japanese were going to attack but failed to act upon this information.
So does this mean it was an intelligence failure in terms of collection? But then again, what info was missed out in terms of collection then?
I think there are two answers to this. There are all kinds of conspiracy theories on how we should have known, since there is evidence that the plan was being hatched 6 months prior to the attack. However it is also reported that on that particular weekend the was no sufficient evidence that an attack was imminent. Rather than toy with that, I'll provide a different perspective, based on the openness of your question.
Pre attack: During the great depression, 1929-1939 Navy Yard Puget Sound underwent an expansion project that included repairing roads and rail tracks. This was followed by an order to build 5 destroyers. The shipyard advantaged the Works Progress Administration which help fund workers to complete the expansion. Some Stats: At the time that Pearl Harbor was attacked, the US Navy had a total of 17 Battleships and 30 destroyers (among other various ships), however only approximately 30% of the Navy fleet was stationed at Pearl Harbor. Japan had a total of 12 Battleships, and the majority of their naval fleet was in submarines (195) destroyers (169) and destroyer escorts (180). The attack damage to the US was 8 Battleships, 3 Cruisers, 3 Destroyers, 1 anti-aircraft and 1 training ship. The Japanese had only a couple (if any) ships ordered to be built by their Navy, and lacked a service hub that could repair several damaged ships at once. Three Strikes: There were two successful waves, which successfully damaged or sank 16 total ships [listed later]. The third wave was supposed to take out the fuel storage, however that failed.
Had the attack waves started on the oil storage the damage would have been irreversibly catastrophic. 4.5 million gallons of fuel sat untouched during the attack.
Given the recent expansion of Puget Sound Naval base they quickly became a repair ground for damaged ships, able to dock and repair efficiently. This base became a key factor and the West Coast hub for Naval repairs. Some of the sunken ships were able to be retrofitted and redeployed quickly.
The attack happened on a Sunday, most Naval offices where closed, and many sailors were on leave for the weekend. Fatalities were lower than they could have been as a result.
Strategical, aiming for the oil storage last, hitting on a Sunday when personal numbers where low, and not accounting for the newly expanded PSNS to repair and redeploy ships, were all missed opportunities of intelligence that would have greatly influenced the outcome.
I know there is a more thorough answer for both sides, but I hope this helps.