Ambush the Ambushers

Converted for the Web from “Battle Of Wits: The Complete Story Of Codebreaking In World War II” by Stephen Budiansky

Yamamoto’s plan was the most elaborate seaborne ambush ever conceived by the mind of man. Five separate forces, a total of two hundred ships and 250 aircraft including eleven battleships, eight carriers, and twenty-three cruisers, would move across a million square miles of the Pacific in a tightly orchestrated plan. While the Northern Force staged a diversion in the Aleutians, the Striking Force with four carriers and two battleships would neutralize Midway’s fighters and bombers, clearing the way for the dozen troopships of the Occupation Force to land five thousand men and seize the island. Meanwhile, a screen of twenty submarines would establish a picket line between Midway and Hawaii to warn when the American carriers sortied from Pearl Harbor to the rescue. That would be the signal for the final act to begin. The Main Body, a huge armada built around seven battleships and a carrier, would hang back hundreds of miles to the west until the American ships committed themselves; it would then spring forward for the kill.

Yamamoto would personally command the operation from the battleship Yamato, the world’s largest, a seventy-two-thousand-ton vessel whose 18.1-inch guns could throw a thirty-two-hundred-pound shell twenty-five miles. An Estimate of Situation issued just before the battle began by Admiral Chuichi Nagumo, commander of the Striking Force, summarized the Japanese plan, and the Japanese confidence in it: “Although the enemy lacks the will to fight, it is likely that he will counterattack if our occupation operations progress satisfactorily…. After attacking Midway by air and destroying the enemy’s shore based air strength to facilitate our landing operations, we should still be able to destroy any enemy task force which may choose to counterattack.”

Nimitz summoned a final staff meeting for Wednesday, May 27, to review his own estimate of situation. Nimitz was prepared to stake everything on Rochefort’s analysis, but it was a huge gamble. It would mean leaving Hawaii defenseless as he rushed his carriers to Midway before the Japanese arrived. Attending the Wednesday morning meeting would be General Delos Emmons, the Army commander in Hawaii, and General Robert C. Richardson, whom Marshall had sent from Washington.

In the meanwhile, Rochefort and one of his staff hit on a scheme they hoped would get the meddlers back at OP-20-G to shut up. While attending engineering school at the University of Hawaii, Lieutenant Commander Jasper Holmes had spent some time at the Pan Am repair facility on Midway. He recalled that all of the island’s water came from a desalination plant. With Nimitz’s approval, Rochefort and Layton on May 19 sent instructions via the undersea cable to Midway. The radio operators there were to send an uncoded “flash” message reporting that the distillation plant was broken. Two days later Tokyo Naval Intelligence sent a signal in JN-25 reporting that “AF Air Unit” had sent a message to Hawaii reporting it had only a two weeks’ supply of fresh water and asking for an immediate resupply. The Japanese signal was broken both by Station Hypo and by the U.S. Navy intercept unit in Melbourne, Australia; Rochefort shrewdly laid low and said nothing. The next day Melbourne forwarded the intercept to Washington with the comment, “This will confirm identity AF.” To keep the Japanese — and Washington — from learning that it had all been a setup, Layton even arranged for Hawaii to send a reply to Midway reporting that supplies were on the way.

Rochefort stayed up all the Tuesday night before Nimitz’s staff meeting going over the months of messages. Disheveled and beat, he showed up half an hour late but was able to avert the wrath of a room full of waiting admirals and generals when he reported that Station Hypo had broken the last remaining piece of JN-25, a separate code-within-the-code used for dates. He then flourished the payoff: a message dated May 26 ordering destroyer escorts for the troopships to depart from Saipan on May 28, proceed at eleven knots, and arrive at Midway June 6. An earlier decrypt had revealed that air attacks against Midway would commence from a point to the northwest of the island on day “N – 12.” That fixed the likely day for the Japanese air assault at June 3 or 4.

That same day, May 27, the Japanese changed both the code book and the additive tables for JN-25 and imposed radio silence on the Midway and Aleutian forces. The code breakers were blacked out. But Nimitz had everything he needed already. He knew where the Japanese would strike and with what forces, he knew when, and he knew exactly what he had to do to get there first.

The fast carrier task force had been born of necessity in the aftermath of Pearl Harbor. With the Battle Fleet crippled, Nimitz had studied his assets and reassembled them as best he could into a fighting force. Despite the manifest success of naval air power at Pearl Harbor, and despite the manifest vulnerability of even battleships to air attack, many traditionalists in the navies of America and Great Britain continued to insist that nothing could take the place of the heavily armored and heavily gunned behemoths. Nimitz boldly rejected that view, assigned the few surviving battleships of the Pacific Fleet to convoy duty between Hawaii and the West Coast, and began perfecting the high-speed hit-and-run techniques that carriers made possible.

Nimitz’s plan for Midway was simplicity itself compared to the baroque evolutions of Yamamoto’s plan: He would get there first and ambush the ambushers. To carry out the mission, he had two task forces available, TF 16, with Hornet and Enterprise, and TF 17, which had been composed of Lexington and Yorktown. But the Battle of the Coral Sea had left the Lexington a flaming wreck on May 7. Yorktown was damaged in the same fight by a bomb that plunged through her flight deck and exploded below. Nimitz now ordered the ship to be repaired and ready for action in three days, a job that in peacetime would have taken three months. Fifteen hundred men worked around the clock, shoring up bulkheads with wooden timbers and doing more patching than repairing, but she steamed out of Pearl on May 30, ready for action.

Meanwhile the marines and airmen on Midway itself braced as best they could. The local Marine commander, a First World War veteran who firmly believed in the efficacy of barbed wire, strung miles of it around the island. There was so much dynamite stockpiled that it finally began to pose more of a threat to the defenders than the attackers; tons were dumped at sea in preparation for the Japanese attack. Briefed on the enemy plan, the island’s commanders were astonished at the level of detail provided. A facetious rumor went around that Tokyo Rose was on the American payroll and sent coded messages in her propaganda broadcasts.

Nimitz’s final orders to his task force commanders instructed them to proceed on the principle of “calculated risk.” The war would never be won by commanders who never took a chance. Just don’t take foolish chances, Nimitz was saying.

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