“You who participated in the Battle of Midway today have written a glorious page in our history.  I am proud to be associated with you” — Admiral Chester W. Nimitz (June 4, 1942).
Having received confirmation that the last of Nagumo’s four carriers had been “last seen burning fiercely,” Nimitz radioed the above message to all of his task force commanders.  The prelude to this glorious page was written largely by the efforts of the officers and men of Station HYPO.  In the preceding weeks and months, Commander Joe Rochefort and his team in the dungeon had successfully navigated dangerous and uncertain waters on the U.S. Pacific Fleet’s path to Midway — but, it wasn’t easy.

Affirm Fox

Following the Battle of the Coral Sea there was much conjecture as to Yamamoto’s next move.  Many believed they would reattempt a strike and occupation of Port Moresby.  Others were convinced that the Japanese were determined to deal another blow to the Pacific Fleet on Oahu.  Others still, feared that the Japanese would be so bold as to strike at the west coast of the United States.  Once again, nobody really knew what to expect — not even the cryptanalysts at Station HYPO who were now able to read a significantly higher volume of the IJN’s main operational code than earlier in the war.

Though HYPO’s cryptanalysts had broken thousands of the JN-25(b)’s 50,000 five-digit code groups, they were still plagued by enough blanks in messages not to be able to paint a complete picture.  When they were able to do so, much of their estimates were called into question by OP-20-G and others.  Fortunately, Joe Rochefort possessed an unrelenting determination that had served him well at many points in his career — and would do so again in the following weeks.  He believed Yamamoto’s interest was in two tiny islands in the middle of the Pacific Ocean — Midway Atoll.

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Eastern and Sand Island of Midway Atoll

As early as March 10, 1942, Rochefort had determined that the Japanese digraph “AF,” or Affirm Fox, equated to Midway.  More recent intercepts had continued to reflect Japanese interest in “AF” as well as indications that the Japanese were preparing for another major offensive.  Rochefort was completely confident in his analysis.  He had convinced Admirals Nimitz and King, but there were still some naysayers whose staunch opposition began to make Nimitz uneasy.  To silence that opposition — and remove any of his own doubts — Admiral Nimitz approved a ruse designed to trick the Japanese into confirming the location of the geographic designator.

HYPO’s Jasper Holmes had devised the ruse assuming that any force intending to occupy the small island would have great interest in the availability of fresh water.  On May 20, 1942, Midway Island radioed to Pearl Harbor, in the clear, that their water-distillation plant had suffered a major casualty.      Japanese forces on Wake Island intercepted the message and radioed to Tokyo that “AF” was short of fresh water.  On May 21st, Rochefort transmitted the following message to OP-20-G in Washington knowing that they had intercepted the previous day’s communications:  “As stated previously, Affirm Fox is confirmed here as Midway.”  Though the ruse had succeeded in settling the “AF” debate, there were still many unanswered questions regarding the impending Japanese action.

HYPO’s Evaluation

Those questions would not remain unanswered for long.  Wednesday morning, May 27, 1942, Nimitz summoned Rochefort to present Station HYPO’s estimate of the situation to a room full of flag and general officers at PACFLT Headquarters.  Carlson writes — “Rochefort presented the following scenario:  Within days the kido butai, composed of four carriers (the Kaga, Akagi, Soryu, and Hiryu) and possibly a fifth, the Zuikaku, supported by three battleships, four to five cruisers, and a destroyer squadron, would approach Midway from the northwest at a bearing of 315 degrees, close to within fifty miles and, beginning at around 7:00 a.m. [on 4 June], launch their planes against Midway’s ground and air defenses.”  Rochefort also told the group that a separate force would attack and occupy the western islands of the Aleutians one day prior on 3 June.  HYPO’s evaluation elicited an explosion of questions and even some doubts by the group.  Nimitz, however, would act on the confidence that he placed in Rochefort’s estimate.

Good Luck and Good Hunting

Whether the Japanese brought five carriers to the fight or four, Nimitz would, once again, be outnumbered. The Commander in Chief had only three carriers at his disposal, the Hornet, Enterprise, and Yorktown — the latter of which had been badly damaged earlier in the month in the Coral Sea.  But Nimitz had two other advantages that were perhaps less apparent:  the element of surprise and Midway Naval Air Station, with its more than eighty warplanes, acting as a fourth carrier of sorts.  Maintaining the former would require a a sound plan and a little bit of luck.

Nimitz plan was relatively simple.  As summarized by Carlson, “under [Operation] Plan 29-42, Spruance would depart Pearl [on 28 May] on board the Enterprise, commanding Task Force 16, consisting of two carriers (the Hornet and Enterprise) supported by five cruisers, one light cruiser, and twelve destroyers, and proceed to an area labeled ‘Point Luck’…a spot 350 miles northeast of Midway.  Assuming the Yorktown could be repaired in time, Spruance would be joined on 2 June by Task Force 17, commanded by Fletcher…supported by two cruisers and six destroyers.”  Admiral Fletcher would command the overall operation.

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Once in position at Point Luck, the task forces were directed to await Nagumo’s arrival and avoid detection so as not to spoil the surprise.  When Nagumo’s kido butai was spotted, Fletcher was to close within striking distance.  The warplanes of the three carriers would launch their attacks when Nagumo was at his most vulnerable:  preparing to recover his own aircraft following initial strikes on Midway.  Such was the plan.  Nimitz visited Admiral Spruance and the Sailors of Task Force 16 on the day of their departure from Pearl Harbor.  His message:  “good luck and good hunting.”

A Major Share of the Credit

On the evening of 3 June, the Aleutians were attacked and occupied by forces from the IJN just as Rochefort had predicted.  Hours later, reports of the first sighting of Nagumo’s kido butai would make their way through the airwaves.  The Japanese were approaching Midway from the northwest at 320 degrees.  Having maintained the element of surprise, aircraft from Midway Atoll and Fletcher’s carriers descended upon the approaching force.  When all was said and done, three of the IJN’s carriers had been sunk and the fourth was “burning fiercely” — never to return to service.

Along with other losses on the American side, the Yorktown would sink to her final resting place in the coming days.  Nevertheless, Nimitz had won the battle and a glorious page in history had been written.  Recorded by many as the “turning point” in the War in the Pacific, the Battle of Midway was undoubtedly one of the most crucial battles to have been fought and won in WWII or any war since.

Indeed, the victory was won through the valiant fighting of the airmen and seamen who went toe-to-toe with the enemy on those three days in June.  But, it would have never been possible without the unceasing efforts of CDR Joe Rochefort and Station HYPO’s team of cryptanalysts, traffic analysts, linguists, and ship plotters.  Shortly following the battle, Nimitz said of Rochefort:  “This officer deserves a major share of the credit for the victory at Midway.”  If one were to ask Rochefort what he thought of such praise, he would have undoubtedly attributed it to his team of cryptologists who, for months, had worked and lived in a place they affectionately called the dungeon.

*Author’s note:

There have been entire books written on the Battle of Midway alone — two of which appear below under my references.  To capture the story in a short series of articles such as this, was no easy feat.  There are so many interesting facets of the story which could not possibly be told here.  I have, by necessity, omitted many details which are truly fascinating aspects of this story.  Many of those details relate to the specific combat action of the battles themselves.  The intent was not to negate the importance of the warfighter in the physical domains, but rather to focus on the contributions of those that enabled such action.

Ever since CDR Rochefort reported as Officer in Charge of Station HYPO almost one year prior to the Battle of Midway, he had always considered his overriding duty to be tracking the Imperial Japanese Navy.  He assigned great importance to his responsibility to provide operationally relevant intelligence to the operational commander.  He further recognized — and his actions proved such — that a relationship with his operational commander required a mutual trust and confidence.  He earned that in his relationship with Nimitz (much of the time through his counterpart and friend, LCDR Edwin Layton).  That relationship, perhaps even more so than the intelligence itself, won the Battle of Midway…for intelligence not acted upon is no intelligence at all.

I have strived to tell the story in a way which meets our mission of celebrating the past, present, and future of naval cryptology.  Though much of the focus herein remains on the intelligence produced by the naval cryptologists of Station HYPO, let us not lose sight of those Sailors and service members who gave their lives acting on that very intelligence.  I hope you have enjoyed reading the “Path to Midway” series as much I have enjoyed researching and writing it.

V/r
David

References:

[1]  Carlson, Elliot.  Joe Rochefort’s War:  The Odyssey of the Codebreaker Who Outwitted Yamamoto at Midway.  Annapolis, MD:  Naval Institute Press, 2011.  Print.  [pp. 91-113]
[2] Symonds, Craig.  The Battle of Midway.  New York, NY:  Oxford University Press, 2011.  Print.
[3] Toll, Ian.  Pacific Crucible:  War at Sea in the Pacific, 1941-1942.  New York, NY:  W. W. Norton & Company, 2012.  Print.