Midway and the Codebreakers Who Let the Navy Set an Ambush

The most decisive naval battle of the twentieth century was won, in no small part, by a man in a bathrobe and slippers. He worked in a windowless basement, he kept strange hours, he did not look like a warrior and he did not carry a weapon. His name was Joseph Rochefort, and the weapon he carried was a pencil.

If you ask most Americans how the Navy turned the Pacific war at Midway, they will tell you about pilots and carriers, and they will be right. But the pilots and carriers were at Midway because a handful of cryptanalysts working in the dark in Pearl Harbor had figured out where the Japanese fleet was going and when. The whole battle was an ambush, and the ambush was made of paper. It is a story about intelligence, about a commander willing to bet a fleet on a hunch from a team of specialists, and about the courage of men who flew into near-certain death. It is also a story about the proper use of secret power in a free republic, a subject on which I have strong views.

Six months after Pearl Harbor

Let me set the scene. By late May 1942 the Japanese Empire had run through the Pacific for six months almost without check. After Pearl Harbor, it took the Philippines, Malaya, Singapore and the Dutch East Indies. The American Navy had taken a small step toward recovery at the Battle of the Coral Sea in early May, a tactical stalemate that blocked a Japanese advance on Port Moresby, but the fleet was still reeling. The Pacific Fleet had perhaps three operational carriers.

Japan's Admiral Isoroku Yamamoto had an ambitious plan. He would strike at Midway, a small atoll at the northwest end of the Hawaiian chain, about 1,300 miles northwest of Oahu. Midway itself was not the real objective. The island was bait. Yamamoto expected the American carriers to rush to defend it, and he planned to ambush them with his own much larger fleet and destroy what remained of the Pacific Fleet in a single decisive battle. A diversion in the Aleutian Islands would help to split the American response. It was a good plan, apart from one thing: the Americans were reading the mail.

Station Hypo

In the basement of the Navy's administration building at Pearl Harbor sat a group of codebreakers, officially the Fleet Radio Unit Pacific, known by its call sign, Station Hypo. Its chief was Commander Joseph Rochefort, a Navy officer who had learned Japanese and spent years in the field of cryptanalysis. His staff worked long shifts in a damp, windowless room, over stacks of intercepted Japanese radio traffic, trying to crack the Japanese naval code that the Americans called JN-25.

The code was not fully broken. In practice, cryptanalysts could read parts of messages, fill in the gaps with context, and track the movement of fleets from patterns in the traffic. By the spring of 1942 Rochefort's team had picked up signs of a large operation being planned. A recurring designation kept showing up in the traffic, the letters "AF," which seemed to be the target of a big strike. The question was what AF was. Rochefort thought it was Midway. Some officers in Washington, in the Navy's own cryptanalysis group, thought it could be somewhere else entirely, perhaps in the Aleutians or the South Pacific. A wrong guess could cost the Navy its last carriers.

The fresh-water ruse

So Rochefort's team set a trap, a delightful one. Midway was an isolated atoll, and its water came from a distillation plant. Someone in the Hypo circle proposed a way to test whether AF meant Midway. The commander at Midway was instructed to send a radio message in the clear, an unencrypted message the Japanese could read, saying that the island's distillation plant had broken down and fresh water was short.

The Americans then listened. Within a short time they heard a Japanese message, which they could partly decode, reporting that "AF" was short of water. That was it. AF was Midway. The experiment was elegant and cost nothing. It is also an example of something dear to conservatives: that a small bit of honest ingenuity can beat a large amount of money. A radio message about a broken water plant did more for the Navy than a battleship.

Nimitz's decision

Now comes the point in the story at which a lesser man would have faltered. The commander in chief of the Pacific Fleet, Admiral Chester Nimitz, had to decide whether to trust Rochefort. The decision was not a small one. If Rochefort was wrong, the Japanese would hit somewhere else and the American carriers would be sitting a thousand miles from the fight. If Rochefort was right, the Navy had a chance to meet the Japanese where it wanted, and to take them by surprise.

Nimitz had Rochefort's analysis, which also pointed to a date for the attack, around June 4 or 5. He believed it. He sent his carriers to an area northeast of Midway, to wait, out of sight and out of range, for the Japanese to arrive. He had in the Pacific only three carriers to put at Midway: the Enterprise and the Hornet in the task force under Rear Admiral Raymond Spruance, who had taken over when Admiral William Halsey was in the hospital with a severe skin condition, and the Yorktown, with Rear Admiral Frank Jack Fletcher in command. Against them came four Japanese fleet carriers, the Akagi, Kaga, Soryu and Hiryu, in a force that also included battleships, cruisers and many other ships.

I cannot resist pausing here for a lesson from the text of the Constitution. In The Federalist No. 70, Alexander Hamilton defends a single executive, and gives a reason that applies exactly to Nimitz's decision: "Decision, activity, secrecy, and despatch will generally characterize the proceedings of one man," and he argues that these qualities weaken as the number of decision-makers grows. A committee would have argued about the evidence. A commander decided. The Founders knew that war is the field where the single responsible head matters most, and they made the president the commander in chief in Article II, Section 2. That is a point to remember when we hear arguments about diffusing responsibility for the use of force.

The Yorktown's repair

One more piece of the ambush has to be told. The Yorktown had been damaged at the Coral Sea in early May. Estimates at Pearl Harbor were that repairing her would take about three months. She did not have three months. When she limped into Pearl Harbor around May 27, Nimitz inspected the damage and told the yard to get her ready in three days. The yard workers swarmed over the ship, welding and patching round the clock, and some of the repair work was completed even as she sailed. She left Pearl Harbor on May 30 and joined the fleet. The shipyard workers did something that the experts had called impossible, because the nation's life depended on it.

It is easy to forget that part of the Midway victory was won by welders and machinists. They are the part of the story that never makes the history books.

June 4, 1942: the torpedo squadrons

The battle opened on June 3 with American planes from Midway making contact with the Japanese transport force, and on the morning of June 4 the Japanese carrier force launched its strike against the island. American bombers from Midway attacked the Japanese carriers, without success. Then the carrier-based aircraft took their turn.

The first American planes to find the Japanese carriers were the torpedo bombers, the slow, obsolete Devastators. They flew in without fighter cover, at low altitude and low speed, into the teeth of the Japanese combat air patrol. Torpedo Squadron 8, from the Hornet, was lost almost entirely: all fifteen planes were shot down, and only one man, Ensign George Gay, survived. The torpedo squadrons from the Enterprise and Yorktown suffered terribly as well. Together the torpedo squadrons scored no hits. They did not seem to have accomplished anything.

But they had. The Japanese fighters were drawn down to sea level to deal with the torpedo planes, and the Japanese ships were manoeuvring to avoid the torpedoes. For a short time the sky above the carriers was open and the fighters were out of position. The torpedo men did not know it, and most of them did not live to learn it. They died buying time for others. I would put their sacrifice in the front rank of American courage in the war, and the historians who study the battle consistently do.

Wade McClusky and the decisive minutes

The next act depended on luck and on a decision. Lieutenant Commander Clarence Wade McClusky was leading the dive bombers from the Enterprise. When he reached the point where the Japanese carriers were expected, the sea was empty. He was running low on fuel. He had to guess, and he could have turned back. Instead he sighted a Japanese destroyer steaming at high speed, apparently trying to rejoin the main force, and he decided to follow its wake. It led him to the Japanese fleet.

At about 10:20 to 10:25 on the morning of June 4, McClusky's dive bombers rolled over and attacked the carriers. At about the same time, bombers from the Yorktown hit another. Within minutes, three Japanese carriers, the Akagi, Kaga and Soryu, were fatally damaged and burning. Their decks were crowded with aircraft that had just been refuelled and rearmed, with bombs and fuel lying about, and the fires were catastrophic. Three of the four carriers were gone in the space of a few minutes.

The fourth, the Hiryu, survived the morning and launched strikes that hit the Yorktown. But in the afternoon American dive bombers from the Enterprise found her and hit her too. By the morning of June 5 she had sunk. Four carriers, the core of the force that had struck Pearl Harbor, were at the bottom.

The loss of the Yorktown

The victory was not free. The Yorktown, hit in the afternoon, was crippled and taken under tow. On June 6 a Japanese submarine, the I-168, slipped in and put torpedoes into her and into the destroyer Hammann, which was alongside, and the destroyer sank quickly. The Yorktown floated through the night and sank on the morning of June 7. The Americans lost about 300 men in the battle, and the Japanese lost around 3,000. Japan also lost a heavy cruiser and a large number of its best aircrews, a loss that proved harder to replace than ships.

I will give you the arithmetic of the carriers. Four Japanese fleet carriers were sunk. One American carrier was lost. That is a ratio of four to one, in a battle in which the Japanese had the advantage in numbers. It is not an accident. It is the result of preparation.

The objection: it was luck

The best version of the sceptical argument runs like this. Midway is a story of luck. McClusky's decision to follow a destroyer worked by chance. The Japanese carriers had their decks full of armed planes at the worst moment. The American torpedo attacks happened to pull the fighters down. A few minutes either way and the story reverses. You cannot build a conclusion about intelligence and preparation on a battle that could have gone the other way.

That deserves a real answer.

First, it is true that luck was a factor, and every careful historian says so. Nobody who tells the story honestly can claim otherwise. War has a great deal of friction.

Second, the luck favoured the prepared side. The Americans were at Midway, in a position to strike first, because of intelligence. Without Hypo, the carriers would not have been northeast of the atoll, and the Japanese would have caught them elsewhere, or not at all. The luck of the dive bombers' arrival came on top of an ambush that had been made. When a prepared side gets lucky, the luck is the interest on the investment.

Third, a few of the most "lucky" parts of the story were not luck at all. The yard workers on the Yorktown did not stumble on a repair. The torpedo squadrons did not wander into the Japanese defences by accident; they went in knowing the odds. McClusky's decision to follow the wake was a judgement call by an experienced commander, and he might well have been wrong. To call the result luck is to take away credit that belongs to the men who made the judgement.

The moral of the codebreakers

Now the question that matters for us. The American government in 1942 was reading the enemy's secret communications, and doing it at scale, in secret. The same power, turned inward, is something conservatives treat with great suspicion, and for good reason. The Fourth Amendment protects "The right of the people to be secure in their persons, houses, papers, and effects" against unreasonable searches and seizures. The right is as old as the Bill of Rights.

The lesson of Midway is not that secret intelligence is always good. It is that it is legitimate when aimed at a foreign enemy in a declared war, with the target clear and the purpose defensive, and that it must be held under accountable control. That is the line that distinguishes the codebreakers at Pearl Harbor from a government that watches its own citizens without a warrant. For a modern argument on where that line falls, The Patriot Act After Two Decades, Two Conservative Verdicts Compared is worth a read. The Navy's cryptanalysts earned their place in the story because they were doing what the Constitution authorises: helping the nation defend itself against a foreign foe.

Rochefort himself did not get his due at the time. Navy politics in Washington caused friction, he was moved to other duties, and he did not receive the high decoration his work deserved until it was awarded posthumously in the 1980s. That is, I think, the most characteristic fate of the best intelligence officers: their success is invisible and their reward comes late, if at all. If you want a picture of what quiet public service looks like, there it is.

What it asks of us

A free people has to know why the great victories happened. Midway was not a miracle, and it was not a stroke of genius from a single commander. It was an intelligence success, a leader who acted on it, welders who finished a ship in days, torpedo crews who flew to their deaths and dive bomber pilots who found a way. The home front that built those carriers is told in The Home Front Built Ships in Days and Became the Arsenal of Democracy. For what came before the battle, The Doolittle Raid Hit Tokyo Four Months After Pearl Harbor From a Carrier Deck and Pearl Harbor on December 7, 1941 Hour by Hour From Radar Blip to Declaration.

The case in brief

1. Station Hypo under Commander Joseph Rochefort read enough of the Japanese naval code to identify "AF" as Midway, confirmed by the fresh-water ruse, and predicted a date near June 4.
2. Admiral Nimitz acted on that analysis, positioned three carriers to ambush the Japanese fleet, and had the damaged Yorktown patched in about three days.
3. On June 4, 1942 the torpedo squadrons were nearly destroyed, but they drew the Japanese fighters down, and Wade McClusky's dive bombers and the Yorktown's left three carriers burning within minutes; the fourth went down the next day.
4. The Navy lost one carrier, the Yorktown, to the four it sank, in a battle where luck mattered but favoured the side that had prepared.
5. Foreign intelligence in wartime, under accountable control, is a lawful defence of the republic, and the Fourth Amendment still protects citizens from the same power turned inward.

What you can do: read the text of the Fourth Amendment, then ask your representative how Congress oversees the intelligence agencies and what protects Americans' own communications.