Sixty-five years ago this week, U.S. forces were locked in the pivotal navy engagement of World War II–the Battle of Midway. Thanks to numerous post-war books, documentaries and even a feature film, many of the events associated with that battle have become legend: the 72-hour “patch” job performed by maintenance crews at Pearl Harbor to get the carrier Yorktown (damaged at the Battle of Coral Sea a month earlier) ready for action; the heroic sacrifice of torpedo bomber squadrons from the carriers Enterprise and Hornet, which were virtually wiped out by Japanese fighters and anti-aircraft fire while attacking the enemy carrier force.

But as every student of the battle knows, the sacrifice of the torpedo bomber crews was not in vain; their attacks prevented enemy carriers from launching strikes against our carriers, and left Japanese fighters unable to engage the American dive bombers that subsequently attacked –and sank–four Japanese carriers. Of course, the fact that the dive bombers actually found the enemy fleet is yet another fateful twist in the saga of Midway; running low on fuel, Navy Lieutenant Commander Wade McCluskey, who was leading the bomber formation, made a critical decision to continue his search for the Japanese carriers, finding them minutes later.

Years later, we learned that much of success at Midway was the result of superb intelligence, much of it produced by the Navy’s Communications Intelligence (COMINT) station at Pearl Harbor, under the leadership of Commander Joseph Rochefort. After Pearl Harbor, Rochefort and his team tackled the arduous task of intercepting, deciphering and analyzing Japanese communications, to provide intelligence on enemy force dispositions and battle plans. Early in the war, Rochefort’s unit (Station HYPO) was aided by other cryptology posts in the Philippines, Singapore, Guam and the East Indies. But with the Japanese advance, the other stations were lost; by the late spring of 1942, the Navy’s code-breaking operation was concentrated largely at HYPO and at Navy headquarters in Washington, D.C.

Despite being undermanned and poorly equipped, Rochefort and his unit made steady progress in penetrating Japanese ciphers and reading enemy message traffic. Yet, even historians often fail to understand how difficult that process really was. In the days before supercomputers and “brute logic” code-breaking techniques, cryptanalysis required brilliant minds, ceaseless dedication, superb language skills and a bit of luck. In the movie Midway Commander Rochefort (played by actor Hal Holbrook) is seen working marathon shifts in HYPO’s basement offices, outfitted in a smoking jacket. There seems to be some support for that potrayal; veterans of Rochefort’s unit remember working up to 36 hours non-stop, in an effort to crack Japanese codes.

By May 1942, the HYPO operation was at its zenith, decrypting and analyzing up to 140 Japanese messages a day–out of literally thousands transmitted by the Imperial Navy alone. But Rochefort and his team had a genuine knack for locating the real kernels of intelligence, a process some ascribe to finding a particular piece of straw in an enormous haystack. Rochefort and his HYPO analysts were the first to identify Midway as the likely Japanese target after Coral Sea engagement. That put him at odds with key figures in the Navy intel establishment in Washington, which believed the next thrust would come in the Aleutians–a view shared by the Chief of Naval Operations, Admiral Ernest King.

In the end, the Commander of the Pacific Fleet, Admiral Chester Nimitz, sided with Rochefort and his analysis, after the Japanese fell for a HYPO-crafted ruse, reporting that “AF” (their designation for Midway) was running out of fresh water. That confirmed that island was indeed the enemy target, and allowed Nimitz to concentrate his limited forces to meet the threat. Rochefort’s team also produced a detailed enemy order-of-battle before the engagement, giving Nimitz and his tactical commanders (Admirals Frank Jack Fletcher and Raymond Spruance) detailed knowledge of the forces they faced.

The accomplishments of Joseph Rochefort and Station HYPO take nothing away from the exploits of the sailors and airmen who actually fought at Midway. But the efforts of the cryptanalysts at Pearl Harbor remind us of the importance of intelligence in preparing and shaping the battlespace. As Admiral Nimitz later remarked, without the information provided by HYPO, the U.S. Fleet could have easily missed the Japanese thrust toward Midway, resulting in the loss of that strategic base, and setting the stage for an enemy invasion of Hawaii. Those events would have forced the a redeployment of our fleet to the west coast, possibly delaying the start of our counter-offensive until late 1943, when the first of the Essex-class fast carriers became available. In that regard, Rochefort and his team not only helped us achieve victory at Midway, they also prevented a second military debacle that would have extended the Pacific War by several years.

Regrettably, the story of Joe Rochefort also reminds us that America doesn’t always appreciate its spooks. In a Navy officer corps dominated by Annapolis graduates and ship drivers, Rochefort was always something of an oddity, a former enlisted man who received a direct commission after earning a college degree. He spent the rest of his career as an intelligence officer, and wasn’t afraid to butt heads with other analysts, or his superiors. Rochefort made a few enemies along the way, and he lost a valuable patron when Captain Laurance Stafford was reassigned as head of the cryptology unit in Washington (OP-20-G). Stafford had personally picked Rochefort to lead HYPO, and provided an important buffer between the Hawaii unit and the Navy brass in Washington.

With Stafford out of the way, Rochefort’s adversaries made their move. Just a few months after his Midway triumph, Commander Rochefort was detached from intelligence duties, and reassigned. At the end of World War II, he was commander of a dry dock on the west coast. Rochefort was finally recognized for his contributions to the Midway victory in 1986–10 years after his death–when he was awarded the President’s National Defense Service Medal, the nation’s highest military award during peacetime.