Studying and understanding the attack on Pearl Harbor, the reasons behind it, and the events leading up to it can be a complicated task. It’s not simply a straightforward matter that starts on the morning of December 7, 1941 and ends two hours later. In order to fully grasp what happened that morning, it’s helpful to know about the events in the months and years that led up to that fateful day. There is a lot of specialized military terminology that’s used in describing these events, including something called a Fleet Problem.

The Fleet Problem most closely associated with the Pearl Harbor attack was Fleet Problem XXI, which took place in April, 1940. It was during this exercise that the naval defense of the Hawaiian Islands was tested.

What is a Fleet Problem?

Vought O2U-2 landing on USS Saratoga (CV-3) during Fleet Problem X, 1930

Vought O2U-2 landing on USS Saratoga (CV-3) during Fleet Problem X, 1930

Fleet Problem is a term used by the US Navy to describe a series of 27 exercises pertaining to naval warfare. Each problem or exercise is meant to test specific aspects of the capabilities and readiness of the Navy’s personnel and ships.

For the US Pacific Fleet, these exercises were fairly commonplace in the lead-up to World War II. In the 1930s up until 1940, many of the Fleet Problems took place in Pacific waters, specifically off Alaska, the Midway Atoll, and Hawaii.

The annual exercises, which were first held in February and March of 1923, were mock battles, sometimes pitting one side as defense and the other in an offensive position against a target. The goal wasn’t necessarily to win but to test formations and tactics in a range of different scenarios. The fleet would be divided into two sides and engage one another. There was no use of live rounds to prevent accidental damage and the waste of valuable shells.

The idea behind these exercises was to consider the many difficult challenges the US Navy could face during combat. Unlike today’s more tightly choreographed training exercises, earlier Fleet Problems were about problem-solving and innovating wartime concepts to overall strengthen the Navy in the event of war.

It’s believed that the free-wheeling nature of these exercises was partially responsible for the Allied victory in the War in the Pacific.

Pearl Harbor and Fleet Problem XXI

Aerial view of Pearl Harbor at the conclusion of Fleet Problem XXI, 3 May 1940

It was meant to test and ready the Navy to repel a Japanese attack, but the lessons learned as a result of Fleet Problem XXI weren’t enough in the face the Japanese onslaught.

The eight-part operation determined that not only was the defense of Pearl Harbor possible, so, too, was the concept that a rival nation might cross the Pacific to launch an attack on it. This was also seen eight years earlier, during Fleet Problem XIII.

The earlier operation began with a scenario that depicted a “militaristic Asian island nation” launching an assault on the US Navy.

Sadly, none of these exercises was enough to prepare the United States for the stunning attack that unfolded on the morning of December 7, 1941.

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