Isoroku Yamamoto - Battle of Midway, June 1942

Battle of Midway, June 1942

Yamamoto's plan for Midway Island was an extension of his efforts to knock the U.S. Pacific Fleet out of action long enough for Japan to fortify her defensive perimeter in the Pacific island chains. Yamamoto felt it necessary to seek an early, offensive decisive battle.

This plan was long believed to have been to draw American attention—and possibly carrier forces—north from Pearl Harbor by sending his Fifth Fleet (two light carriers, five cruisers, 13 destroyers, and four transports) against the Aleutians, raiding Dutch Harbor on Unalaska Island and invading the more distant islands of Kiska and Attu. Recent scholarship using Japanese language documents has revealed it was, rather, an unrelated venture of the Naval General Staff which Yamamoto agreed to conduct concurrently with the Midway operation, in exchange for the latter's approval.

While Fifth Fleet attacked the Aleutians, First Mobile Force (4 carriers, 2 battleships, 3 cruisers, and 12 destroyers) would raid Midway and destroy its air force. Once this was neutralized, Second Fleet (1 light carrier, 2 battleships, 10 cruisers, 21 destroyers, and 11 transports) would land 5,000 troops to seize the atoll from the American Marines.

The seizure of Midway was expected to draw the American carriers west into a trap where the First Mobile Force would engage and destroy them. Afterward, First Fleet (1 light carrier, 7 battleships, 3 cruisers and 13 destroyers), in conjunction with elements of Second Fleet, would mop up remaining American surface forces and complete the destruction of the Pacific Fleet.

To guard against mischance, Yamamoto initiated two security measures. The first was an aerial reconnaissance mission (Operation K) over Pearl Harbor to ascertain if the American carriers were there. The second was a picket line of submarines to detect the movement of the American carriers toward Midway in time for First Mobile Force, First Fleet, and Second Fleet to combine against it. In the event, the first was aborted and the second delayed until after American carriers had sortied.

The plan was a compromise and hastily prepared (apparently so it could be launched in time for the anniversary of Tsushima), but appeared well thought out, well organized, and finely timed when viewed from a Japanese viewpoint. Against four carriers, two light carriers, 11 battleships, 16 cruisers and 46 destroyers likely to be in the area of the main battle the Americans could field only three carriers, eight cruisers, and 15 destroyers. The disparity appeared crushing. Only in numbers of carrier decks, available aircraft, and submarines was there near parity between the two sides. Despite various frictions developed in the execution, it appeared — barring something extraordinary — Yamamoto held all the cards.

Unfortunately for Yamamoto, something extraordinary had happened. The worst fear of any commander is for an enemy to learn his battle plan in advance, which was exactly what American cryptographers had done, thanks to breaking the Japanese naval code D (known to the U.S. as JN-25). As a result, Admiral Chester Nimitz, the Pacific Fleet commander, was able to circumvent both of Yamamoto's security measures and position his outnumbered forces in the exact position to conduct a devastating ambush. By Nimitz's calculation, his three available carrier decks, plus Midway, gave him rough parity with Nagumo's First Mobile Force.

Following a foolish nuisance raid by Japanese flying boats in May, Nimitz dispatched a minesweeper to guard the intended refueling point for Operation K near French Frigate Shoals, causing the reconnaissance mission to be aborted and leaving Yamamoto ignorant of whether Pacific Fleet carriers were still at Pearl Harbor. (It remains unclear why Yamamoto permitted the earlier attack, and why his submarines did not sortie sooner, as reconnaissance was essential to the success of MI.) He also dispatched his carriers toward Midway early, and they passed the intended picket line force of submarines en route to their station, negating Yamamoto's back-up security measure. Nimitz's carriers positioned themselves to ambush the Kido Butai (Striking Force) when it struck Midway. A token cruiser and destroyer force was sent toward the Aleutians, but otherwise Nimitz ignored them. 4 June 1942, days before Yamamoto expected them to interfere in the Midway operation, American carrier-based aircraft destroyed the four carriers of the Kido Butai, catching the Japanese carriers at an especially vulnerable moment.

With his air power destroyed and his forces not yet concentrated for a fleet battle, Yamamoto attempted to maneuver his remaining forces, still strong on paper, to trap the American forces. He was unable to do so because his initial dispositions had placed his surface combatants too far from Midway, and because Admiral Raymond Spruance prudently withdrew to the east in a position to further defend Midway Island, believing (based on a mistaken submarine report) the Japanese still intended to invade. Not knowing several battleships, including the powerful Yamato, were on the Japanese order of battle, he did not comprehend the severe risk of a night surface battle, in which his carriers and cruisers would be at a disadvantage. However, his move to the east did avoid the possibility of such a battle taking place. Correctly perceiving he had lost and could not bring surface forces into action, Yamamoto aborted the invasion of Midway and withdrew. The defeat marked the high tide of Japanese expansion.

Yamamoto's plan for MI has been the subject of much criticism. Many commentators state it violated the principle of concentration of force, and was overly complex. Others point out similarly complex Allied operations (such as Operation MB8) that were successful, and note the extent to which the American intelligence coup derailed the operation before it began. Had Yamamoto's dispositions not denied Nagumo adequate pre-attack reconnaissance assets, both the American cryptanalytic success and the unexpected appearance of Fletcher's carriers would have been irrelevant.