What would Japan face if the United States fortified Pearl Harbor after Taranto and kept its defenses on a war footing?
Short answerA much harder target, though poorly concentrated or ranged defenses could still be overwhelmed through gaps in their coverage.
NotesA fully alerted and strengthened Pearl Harbor would create a much harder Japanese problem. Possessing radar and anti-aircraft guns still would not guarantee their effective arrangement. The location and range of the defenses could leave exploitable approaches, as happened at Singapore. The counterfactual depends on the geometry and readiness of the air-defense system as much as its equipment totals.