How 'the first Pearl Harbor' convinced the Japanese they could pull off a similar attack on the US

• In fall 1940, the British faced a dire situation in the Mediterranean, where Italy's large fleet posed an acute threat.
• To neutralize that threat, the British navy mounted a daring aerial attack on the Italian ships while they sat in port.
• The success of the raid at Taranto allowed the British to dominate the Mediterranean and gave the Japanese an idea for a similar attack on the US a year later.

By early spring 1941, Japanese military strategists were hard at work planning their blitz into Southeast Asia. The planners, especially Adm. Isoroku Yamamoto, knew this expansion was only possible if Western countries, particularly the US, were unable to resist.

Japan needed to ensure the US Navy's Pacific Fleet could not interfere. Japanese officials decided on a surprise attack on US Navy ships at Pearl Harbor, knocking them out and buying time for to achieve their other objectives.

Though ambitious, Yamamoto had good reason to believe the attack would succeed: A little over a year earlier, the British conducted a similar attack on the Italian navy at the port of Taranto.

The British operation — the first all-aircraft ship-to-ship naval attack in history — crippled Italy's navy and proved that torpedo attacks on ships in port were possible.

Italy's imposing fleet

The situation in the Mediterranean was quite tense for the British by fall 1940.

The North Africa Campaign against the Nazis was also well underway, but France's surrender to Germany in June meant Britain no longer had the French navy's support. Italy also invaded Greece in October that year, further pressuring the British. (The Germans joined Italy's side in Greece in early 1941, eventually forcing a British retreat.)

The Royal Navy's small Mediterranean force faced Italy's Regia Marina — then the fourth largest navy in the world. The British were stretched thin, and getting supplies to Malta, an island strategically located in the middle of the Mediterranean, was proving difficult.

Particularly worrisome for the British was the Italian fleet at the port of Taranto in southeastern Italy. It included all of Italy's six battleships as well as 16 cruisers and 13 destroyers.

Despite numerical superiority, the Regia Marina declined to meet the British in a decisive, large-scale engagement. This forced the Royal Navy to always operate as a single unit, fearing that if its forces split, they could be picked off.

The British decided they had to take the fight directly to the Italians.

A first-of-its-kind operation

The British selected Taranto as a potential target before the war had even begun, deciding that a night-time air raid would be the most effective attack. The plan called for the carriers HMS Illustrious and HMS Eagle and their escorts to sail with a convoy to Malta to deceive the Italians.

The carriers would then sail to a point 170 miles from Taranto, where 32 Fairey Swordfish torpedo bombers — an old fabric-covered biplane widely considered obsolete — would launch in two waves to attack the Italian warships with torpedoes and bombs.

The Swordfish were modified with an additional fuel tank, which took the place of one of the three crew members. Some also carried flares to light the area for other pilots.

This would be the first time enemy ships were attacked in port by torpedo bombers, which was considered impossible due to a port's shallow waters and the hundreds of machine and anti-aircraft guns that were usually present.

The attack was scheduled for October 21 but was delayed by a fire aboard Illustrious. Eagle's fuel system also suffered failures that prevented it from joining the attack.

The attack

The attack was rescheduled for November 11, with the British force sailing from Alexandria on November 6. With Eagle out, the strike force was reduced to 21 Swordfish, five of which were transferred from Eagle.

The first wave of 12 aircraft arrived just before 11:00 p.m. In a stroke of luck, the Italians had removed some of their torpedo nets because of a scheduled gunnery exercise. The remaining nets didn't reach the harbor floor, meaning British torpedoes could pass under them.

Half the Swordfish carried torpedoes and the other half bombs. After flares were dropped, the harbor erupted in anti-aircraft fire. The Swordfish flew at near-wave height, forcing the Italians to risk shooting their own ships.

The first wave hit two battleships with torpedoes. A number of cruisers and destroyers were also hit with bombs, and a nearby oil-storage facility and seaplane base were also attacked. One Swordfish was shot down and its crew captured.

The second wave of nine aircraft arrived almost an hour later. They torpedoed a third battleship and hit one of the previously damaged ones. Another Swordfish was shot down, killing its crew. Other planes carrying bombs hit several other ships, causing various degrees of damage.

A crippled fleet and a blueprint for Japan

The attack crippled Italy's navy. Three battleships — Littorio, Caio Duilio, and Conte di Cavour — were resting on the harbor floor. Littorio and Caio Duilio would take months to repair, while Conte di Cavour never returned to service.

Two cruisers and two destroyers were also damaged, over 50 sailors were killed, 600 were wounded, and the oil facility was wrecked.

In just two hours, a handful of obsolete British torpedo bombers disabled half of Italy's battleships. The rest were forced to operate out of ports farther north, making them less of a threat to the Royal Navy, which now dominated the Mediterranean.

Prime Minister Winston Churchill told Parliament in a speech that the attack "carries with it reactions upon the naval situation in every quarter of the globe."

Within days of the attack, Lt. Takeshi Naito, an assistant air attaché at the Japanese Embassy in Berlin, arrived in Taranto to investigate. A larger Japanese military delegation followed in the spring and made an extensive report.

A little more than a month before Japan's attack on Pearl Harbor, Naito met with Cmdr. Mitsuo Fuchida, who would lead the air attack on the US base. They discussed Taranto at length.

After the war, Naito recalled "the most difficult problem [at Pearl Harbor] was launching torpedoes in shallow water. The British Navy attacked the Italian fleet at Taranto, and I owe very much for this lesson in shallow-water launching."

The US Navy also had an expert at Taranto. Lt. Cmdr. John Opie, an assistant naval attaché at the US Embassy in London, was actually aboard Illustrious as an observer during the attack.

Opie quickly wrote a report and even requested to visit Pearl Harbor to discuss what he had learned. But his requests were ignored, and in December 1941, Japan would conduct their own Taranto, sinking or damaging 19 US Navy ships and killing more than 2,000 Americans at Pearl Harbor.