The Battle of Midway was the turning point in the Pacific theater of operations during World War II. Key to Admiral Chester Nimitz’s decision to engage the Japanese at Midway were the seminal efforts of the U.S. Navy’s codebreakers.
“The one thing that stands out in my vivid memory was the Battle of Midway. As a very new ensign I was part of an organization that developed the intelligence for this battle, I saw that develop day by day, I helped with it.” — Station Hypo veteran Rear Admiral Donald “Mac” Showers (August 25, 1919 – October 19, 2012)
Midway’s Place in History
America needed to win. Just six months after the attack on Pearl Harbor, the Japanese were poised to press their advantage, destroy what was left of the Pacific Fleet, and threaten the West Coast of the United States. Our outpost at Midway stood between the Imperial Japanese Navy (IJN) and Hawaii.
Facing VADM Nagumo’s IJN strike force of two battleships and four carriers (Akagi, Kaga, Hiryu and Soryu), the U.S. Navy engaged with no battleships and three carriers — USS Enterprise (CV 6), USS Hornet (CV 8) and USS Yorktown (CV 5) — the latter having been heavily damaged and hastily repaired after the Battle of Coral Sea (May 4-8, 1942).
In the action at Midway, Japan lost four carriers, a heavy cruiser, three destroyers and 256 planes. The Americans lost Yorktown, a destroyer and 145 planes. When combined with its earlier losses at Coral Sea, the IJN’s defeat at Midway shifted the balance of power in the Pacific decidedly toward the United States. Japan was never able to recover.
Information Superiority Paved the Way for Victory
Admiral Nimitz’s success at Midway was due in great part to his foreknowledge of the IJN’s disposition and intentions. Having penetrated Japanese naval codes as far back as the 1930s, U.S. Navy radio intelligence specialists and Japanese linguists in Melbourne, Australia and Pearl Harbor combined radio traffic analysis techniques and a deep understanding of IJN tactics to provide predictive awareness at Midway.
In early 1942, cryptologists under CDR Joe Rochefort at Pearl Harbor’s Station Hypo detected Japanese references to a pending operation against an objective designated “AF.” Fleet Intelligence Officer, CAPT Edwin Layton and Rochefort believed “AF” to be Midway. To confirm, they arranged for Midway’s installation commander to send an unencrypted message falsely indicating problems with its fresh water condenser. When Station Hypo subsequently intercepted a Japanese intelligence report citing “AF is short of water,” Midway was confirmed as the target and Admiral Nimitz suddenly enjoyed decision superiority. As a consequence, he was able to position his forces to surprise and defeat the Japanese fleet.
Working in the shadows to decipher, understand and predict Admiral Yamamoto’s next steps, these previously unknown and unheralded information experts pioneered Information Warfare as we know it today.
Thanks to American codebreakers, judicious aircraft carrier tactics and providential timing, the U.S. Navy inflicted a devastating defeat on the Japanese navy at Midway.
The Battle of Midway demonstrated the importance of a commander’s basic insight into what was actually occurring on, below, and above the sea. Today we call that “Battlespace Awareness,” one of the key tenets of Information Warfare, along with “Assured Command and Control” and “Integrated Fires.”
Fast Facts and Figures
- The IJN lost four large carriers, more than 100 pilots and more than 700 aircraft mechanics at Midway.
- JN-25, the Japanese code, consisted of approximately 45,000 five-digit numbers, each representing a word or phrase.
- 3,000 miles — According to General George C. Marshall, U.S. Army Chief of Staff, “…as a result of cryptanalysis we were able to concentrate our limited forces to meet their naval advance on Midway when we otherwise would have been 3,000 miles out of place.”
Original publication June 2016.