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The Battle of the Coral Sea and the Unveiling of Magic: May 1942

BA University of Arkansas (Fayetteville) Geography & History

Japan's Navy Threatens Australia : Coral Sea May 1942

The struggle for control of the Coral Sea was the first battle where neither side saw each other, and was the first major naval engagement in history between two carrier forces. The Japanese planned to capture Port Moresby, the capital of New Guinea, in order to provide a forward operating base for future attacks on the Australian mainland. They were sure that ultimate victory was just within their grasp. Why not? In the past six months Japan's military had succeeded in one daring attack after another.

The Japanese invasion of New Guinea was under the command of Vice-Admiral Shigeyosh. The plan was comprised of three convoys that were to advance out of Truk and Rabaul, then head to three different locations, the largest heading to Port Moresby and the others to set up sea-plane bases on the Island of Tulagi and in the Louisides Archipelago.

Protecting these convoys was a covering force commanded by Rear-Admiral Goto Aritomo. Under his command were four heavy cruisers, one destroyer, and one light carrier, the Shoho. There would also be another a strike force including the two large carriers Shokaku and the Zuikaku along with two heavy cruisers. This would give the Japanese navy an over-whelming advantage over the Americans in the upcoming battle.

At this point in the war the United States decided implement a weapon of immense power given the proper code name "Magic". Colonel William Friedman, founder of the United State Signal Intelligence Service since 1922, one of the most talented living cryptanalysts gave American leaders the ability to read the cipher in which Japanese diplomatic signals were transmitted around the globe. It would literally give American generals a chance to look over the shoulders of their enemy. Magic was so black it wasn't declassified until forty years after the end of the Second World War.

Not only had Friedman's team, which included his wife, cracked the cipher itself, by a remarkable technical feat machines were constructed on which enciphered Japanese signals could be returned to their text. By reading these communiques American leaders were now able to be one step ahead of the enemy. Once Japanese intentions were made clear, Admiral Chester Nimitz immediately sent an carrier task force to the Coral Sea to block the Japanese advance toward Australia completely catching them off balance.

The Battle for the Coral Sea

On May 3,1942, a Japanese force landed on Tulagi in the Solomon Islands. The Japanese commanders were supremely confident they would crush any American naval force south of New Guinea and the Solomon Islands. American Vice Admiral Frank J. Fletcher commanding Task Force 17 was already operating in the Coral Sea. His task force was supported by warships from Australian and New Zealand. Once they were informed of the Japanese attack they sailed north-westwards heading for Port Moresby to thwart the Japanese attack.

A confused battle took place, but aircraft from the USS Lexington sighted the Japanese carrier Shoho first and sank her. Afterward, the Japanese carrier force sent a counter-strike to eliminate the threat. Japanese aircraft mistakenly thought they had found the American carrier force, instead sank a destroyer and a tanker.

On May 8, 1942, the Americans and the Japanese launch repeated strikes against each other. Aircraft from the Yorktown managed to damage the large fleet carrier Shokaku enough to render her incapable of launching any more planes, while the Japanese hit both the Yorktown and the Lexington.

The Japanese, left unable to protect their invasion fleet, decided to withdraw from Port Moresby, much to the disappointment of Admiral Yamamoto. The American carrier Lexington, which at first appeared to recover from the Japanese air- attack, suddenly began to sink after explosions engulfed the ship caused by leaking fuel.

The Battle of the Coral Sea was a partial success for the Americans since it prevented a Japanese invasion of New Guinea near Port Moresby, while the Japanese were convinced they had given the Americans a "beating" sinking two of their carriers. Unknown to Yamamoto and his commanders the American carrier Yorktown managed to limp back to Pearl Harbor for repairs. It would play a major role in the American victory at Midway in June of 1942.

The USS Yorktown

The American carrier USS Yorktown conducts aircraft operations in the Pacific sometime before the battle for the Coral Sea.

The American carrier USS Yorktown conducts aircraft operations in the Pacific sometime before the battle for the Coral Sea.

Magic: America's Trump Card

The United States Army Signals Intelligence Section (SIS) and the Navy Communication Special Unit worked in tandem to monitor, intercept, decode, and translate Japanese messages. Commander Joseph Rochefort, the chief cryptanalyst at Pearl Harbor, had helped break the Japanese naval code in 1940. An unconventional officer, usually attired in carpet slippers and a red smoking jacket, Rochefort had not been able to warn of the attack on Pearl Harbor due to strict radio silence imposed on the Japanese attack force.

Fortunately for the United States Navy, Rochefort had now learned to decode a signal which revealed that the Japanese were planning to land on the south-eastern tip of New Guinea, and seize the airfield at Port Moresby. Occupying New Guinea would give the Japanese free reign from the air and sea over the shipping lanes between the United States and Australia. This move would starve Australia of much-needed supplies, and enable Japan's armed forces to attack northern Australia at will.

With the help of the cryptanalyst from Magic the American navy will be waiting for the Japanese in an epic battle that would change the balance of power in the Pacific. With the sea lanes to Australia secure American General Douglas MacArthur would use it as a launching point in his bid to re-take the Philippines two years later. With their shipping lanes now threatened Japan's military was forced to take the defensive.

Unknown to the American soldiers fighting and dying on the front lines against the Japanese, cryptanalysts under the code name "Magic" had helped changed the course of history. The ability to decipher and read Japanese communications was one of the key components of the Allied victory in the Pacific.

Commander Joseph Rochefort

Commander Joseph Rochefort, chief cryptanalyst at Pearl Harbor, helped break the Japanese naval code before the Battle for the Coral Sea.

Commander Joseph Rochefort, chief cryptanalyst at Pearl Harbor, helped break the Japanese naval code before the Battle for the Coral Sea.

Satellite view of the Louisiade Archipelago were the Battle for Coral Sea (May 1942) would take place. The battle would occur over a vast empty body of water. Only those who took part in the battle would witness the events.

Satellite view of the Louisiade Archipelago were the Battle for Coral Sea (May 1942) would take place. The battle would occur over a vast empty body of water. Only those who took part in the battle would witness the events.

William Frederick Friedman one of the most brilliant cryptanalysts of the twentieth century. He would lead the effort to break the Japan's famous Purple machine.

William Frederick Friedman one of the most brilliant cryptanalysts of the twentieth century. He would lead the effort to break the Japan's famous Purple machine.

Sources

Lewin, Ronald. Ultra Goes to War. McGraw-Hill Book Company 1325 Avenue of the Americas New York, NY 10019. 1978

Swanston, Alexander. The Historical Atlas of World War II. Chartwell Books,276 Fifth Avenue Suite 206 New York, New York 10001. 2010

© 2021 Mark Caruthers

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