In preparing for the Dec 7, 1941 attack on Pearl Harbor, the Japanese Navy studied closely a similar operation carried out by ...whom?

When planning the Pearl Harbor attack several Japanese naval officers had been impressed by the British Operation "Judgment" that took place on the night of 11–12 November 1940. Under Admiral Andrew Cunningham the Royal Navy launched the first all-aircraft ship-to-ship naval attack in history, employing 21 outdated Fairey Swordfish biplane torpedo bombers from the aircraft carrier HMS Illustrious in the Mediterranean Sea.

The attack struck the battle fleet of the Italian Regia Marina at anchor in the harbor of Taranto (southern Italy) using aerial torpedoes despite the shallow depth of the water. The devastation wrought by the British carrier-launched aircraft on the large Italian warships was the beginning of the ascendancy of naval aviation over the big guns of battleships.

Admiral Yamamoto even dispatched a delegation to Italy, which concluded that a larger and better-supported version of Cunningham's strike could force the U.S. Pacific Fleet to retreat to bases in California, thus giving Japan the time necessary to establish a "barrier" defense to protect Japanese control of the Dutch East Indies.