The US Unknowingly Predicted Pearl Harbor Years Before It Happened

Japanese Attack on Pearl Harbor, December 7, 1941. Battleship row in flames. (Artwork by John Hamilton / U.S. Navy Art Gallery)

The attack on Pearl Harbor is one of the most pivotal moments of the 20th century, and even in human history. This attack brought the U.S. into the war, leading to the nation squeezing every ounce of potential out of its enormous industrial and technological capabilities, culminating in mankind harnessing the power of the atom. The attack has remained a hot topic worldwide for the total surprise of the attack, and the notion that the Japanese inadvertently woke the “sleeping giant” that was the U.S.

The attack’s objective was to try and knock out the U.S. Pacific Fleet in one swing to allow the Japanese to move through the Pacific uninhibited before the U.S. could rebuild its fleet, and then force a peace agreement. Japan was aware that anything less than the complete destruction of U.S. naval forces would result in their eventual defeat.

The attack shocked the U.S. people, changing their previously hesitant stance on joining WWII into overwhelming support. By the next day, the U.S. had formally entered the war.

But at the time, was the attack such a surprise to the U.S. government?

Did the U.S. know it was coming?

The attack on Pearl Harbor is one of the most analyzed American military actions, both officially, with 10 government inquiries, and by historians. As with any major historical event, like the assassination of JFK or the September 11 attacks, the attack on Pearl Harbor is rife with conspiracy theories.

The most popular is the U.S. was aware of the impending attack and let it happen to justify the nation’s entry into WWII. One of the earliest examples of this idea was written out in a booklet by the co-founder of the America First Committee, John T. Flynn, in 1944. The America First Committee was against the U.S. joining the war.

People marching in protest against the United States joining the war in Europe circa 1941 in New York, New York. The AFC was the pressure group against the Americans joining World War II.
America First Committee march. (Irving Haberman/IH Images/Getty Images)

In this booklet, named The Truth About Pearl Harbor, Flynn detailed what is now known as the “advance-knowledge conspiracy theory.”

Before the attack, the U.S. had made good work breaking Japanese military and diplomatic codes. Because of this, it’s easy to assume the U.S. would have intercepted communications about the attack long before it began. The U.S.’s carriers not being present at the time of the attack is another point that adds fuel to the fire.

While the bulk of these theories have been debunked, they are spurred on by the number of official documents relating to the attack that remain classified. Many believe these contain the missing information that proves the U.S. was aware of the attack.

WWII Recruiting Poster "remember pearl harbor - enlist now"
WWII Recruiting Poster.

In all likelihood, the U.S. was aware an attack was coming, just not where or when. The aircraft carriers not being at Pearl Harbor doesn’t mean much, as the main targets were battleships. At the time, battleships were regarded as the most dominant and prestigious tool in a fleet’s arsenal. In addition, U.S. codebreakers were able to intercept and read Japanese communications, but not all of them. And disorganization among codebreaking departments would have made establishing an exact time and date for an attack extremely difficult.

The U.S. not knowing the attack was coming is also backed up by their naval actions in the Atlantic Ocean at the time, which were, if anything, leaning much more towards a war with Germany.

However, despite not knowing, the U.S. should, and could have been much more prepared for a potential attack.

The U.S. naval exercises that predicted the attack on Pearl Harbor

Long before the day that would live in infamy, the U.S. and Japan were sizing each other up. In fact, the U.S. was so concerned that they drew up War Plan Orange, essentially an instruction manual on fighting a war against the Japanese. Unfortunately, this plan relied on outdated tactics and technology.

As part of their planning, the U.S. conducted mock battles in the Pacific to identify weaknesses in their defenses. On February 7th, 1932, a particularly interesting mock battle took place, at none other than Pearl Harbor.

Admiral Harry E. Yarnell, who first showed Pearl Harbor was vulnerable to attack
Admiral Harry E. Yarnell.

The attack, named Fleet Problem Number 13, was commanded by Rear Admiral Harry Yarnell, and was meant to simulate an attack from a “militaristic, Asian, island nation” on the major military installation. Yarnell was an experienced leader and a qualified pilot, a rarity at the time.

He adopted tactics that he believed the Japanese were likely to use, stating they “had always started operations by attacking before a declaration of war.” He also knew Pearl Harbor assumed an attack would be spearheaded by battleships, so he left these behind and used two aircraft aircraft carriers instead, Lexington and Saratoga.

aerial photograph of Pearl Harbor, Hawaii (USA), from 5,250 m (17,200 ft) altitude, looking directly down on East Loch and on the Fleet Air Base on Ford Island. Taken on 3 May 1940, after the conclusion of Fleet Problem XXI
Aerial view of Pearl Harbor, 1940. (Photo Credit: U.S. Navy)

He launched a surprise aerial attack with 152 aircraft armed with bags of flour instead of bombs, and attacked both the airfield and battleship row. His attack was declared a complete success.

The brass in charge of defending Pearl Harbor were embarrassed and refused to admit defeat. They claimed that Yarnell’s early Sunday morning surprise attack came at an “inappropriate” time and that it was unfair.

They also argued, with logic that is unbelievable today, that the Japanese would never have been able to drop bombs with such accuracy becauseĀ “everyone knew that Asians lacked sufficient hand-eye coordination to engage in that kind of precision bombing.”

The judges of the battle received pressure from the War Department, and eventually named Pearl Harbor the victor.

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This battle is almost exactly what would happen a decade later, but for real and on a much larger scale. If these very clear vulnerabilities in the harbor’s defenses had been addressed, would the Japanese have achieved victory on December 7th 1941? No one can know for certain. But what is for certain is that the answer to that question will be debated for years to come.