This continues a series at the Diplomat on significant counterfactual scenarios in Asian history. See the first installment onChiang Kai-shek’s victory in the Chinese civil war and the second on theUnited States using nuclear weapons during the Korean War.

There is a story—probably apocryphal—that wargamers at the U.S. Naval War College in Newport, Rhode Island, have replayed the 1942 Battle of Midway many times. Apparently, the Americans always lose. Almost more than any other during the Second World War, this battle was won due to a fortunate combination of good intelligence, planning, and, most of all, luck. The U.S. Navy was far inferior to its Japanese counterparts in terms of numbers and experience but was still able to sink all four of the Imperial Navy’s committed aircraft carriers. This marked the beginning of the long, grueling allied island-hopping advance in the Pacific, which eventually culminated in Japan’s defeat over three years later.

The Battle of Midway remains a well-known and cherished memory in U.S. military history. InThe Collected What If?, Theodore F. Cook Jr., at the William Paterson University of New Jersey, gives a great account of how there are several points both before and during the battle that history easily could have taken a different path. In June 1942, Imperial Japan had reached the zenith of its conquests. The Japanese Empire stretched from China to Wake Island, from the Aleutians to Indonesia. It had decimated the U.S. Navy at Pearl Harbor (although, crucially, U.S. aircraft carriers were out of port and escaped attack), conquered all European and American colonies in Southeast Asia, and overrun the U.S. Army in the Philippines. Although the Japanese and American navies had fought an inconclusive battle at the Coral Sea, in which each side lost an aircraft carrier, the Imperial Navy retained the strategic initiative.

The Coral Sea episode indirectly resulted in two advantages for the Americans. Firstly, it prevented the Japanese from occupying Port Moresby in Papua New Guinea, which could have allowed the Imperial Navy to execute their planned Operation FS, the occupation of Fiji and Samoa. This could have critically isolated Australia, diverting allied resources away from other theaters in the Pacific. Most importantly, it removed two Japanese aircraft carriers from participating at the Battle of Midway (the IJN Shokakuand IJN Zuikaku which bothhad to return to Japan for repairs and replacement of its fighters lost at the Coral Sea, respectively. The U.S. lost the carrier USS Lexington, while the USS Yorktown suffered critical damage and was believed to be sunk by the Japanese.)

With the Imperial Navy’s southwestern offensive stalled at the Coral Sea, Admiral Yamamoto Isoroku looked to “plug the gaps” in Japan’s geostrategic cordon. First, this meant securing the northern flank by occupying the Aleutian Islands of Attu and Kiska. However, the most important objective was the island of Midway, which hosted a large U.S. military presence. Midway allowed the U.S. to project power throughout the Central Pacific, by offering anchorage to its submarines and aircraft carriers. If the island were to fall to Japan, the Imperial Navy and Air Force could turn that projection around, towards Hawaii and the U.S. western coast.

However, the Americans were well-informed of Japanese intentions. Due to the efforts of the Navy’s Combat Intelligence Unit (known as “HYPO”), Admiral Chester W. Nimitz’s staff knew that the Japanese were planning another offensive. HYPO had been able to partially decipher the Imperial Navy’s JN-25 code, which revealed that the geographical location known as “AF” was the target for the Japanese attack. In order to uncover the location behind “AF,” the U.S. garrison on Midway sent a fake plain-text radio message saying that the island was running out of water. When Allied listening stations in Australia picked up a Japanese radio message saying that “AF” was running out of water, Nimitz knew that Midway was the intended target for the Japanese attack.

The U.S. Navy was therefore able to spring a trap on the Japanese fleets approaching Midway. As they believed the U.S. fleet to be in Pearl Harbor, recuperating after the Coral Sea, the Imperial Navy was in a rush to take Midway before American reinforcements could arrive. As a result, Admiral Nagumo Chuichi didn’t post a picket line of submarines to provide early warning of the U.S. fleet’s movements. As the Japanese aircraft were refueling and rearming after their initial bombing run on Midway, Admirals Jack Fletcher and Raymond Spruance were able to catch the Imperial fleet by surprise. Attacking from a flanking position named “Point Luck” and, informed of the Japanese movements by submarines, the Japanese lost all four of their committed carriers, in exchange for one out of three American (the U.S.S.Yorktown, hastily repaired after its heavy damage in the Coral Sea). Almost as critical as the destruction of the Japanese carriers was the loss of its experienced aircrews and sailors. From this victory, the Americans were able to gain the strategic initiative, starting with the landings at Guadalcanal in August 1942.

The first order counterfactual in this scenario takes place before the battle began. As we have seen, the United States was able to surprise and defeat the Imperial Navy due to the clever use of disinformation. What if the Japanese radio operator who intercepted Midway’s water shortage message had turned to his superior officer and asked “Why are they sending this in the clear? Don’t they care that we know that Midway is running out of water?” With a bit of imagination, Japanese intelligence analysts could have, or even should have, guessed that this was a deliberate attempt at deception on the part of the United States.

Our second order counterfactuals start here. Yamamoto could either have called off the attack on Midway, choosing other targets for Japan’s aircraft carriers; perhaps a renewed offensive towards Fiji, Australia, or Dutch Harbor in Alaska. However, as Cook argues, he was well aware of the necessity of dealing a critical blow to the U.S. Pacific Fleet in order to keep the strategic initiative. It is more likely that he would have attempted to set his own trap against the United States at Midway. In accordance with the Imperial Navy’sKantai Kessen, or decisive battle doctrine, Yamamoto and the Imperial Navy’s general staff could hope to draw the remaining U.S. carriers into a decisive battle. With the U.S. Pacific Fleet removed and Hawaii under threat, Yamamoto hoped that the U.S. would sue for a negotiated peace, securing Japan’s conquests in Asia.

Calculating that two, or perhaps three U.S. carriers opposed him, Yamamoto could count on superiority in numbers. (The Japanese thought the USS Yorktownhad been sunk or disabled in the Coral Sea and the whereabouts of the last American carrier in the Pacific, the USS Saratoga was unknown.) If they knew, or strongly suspected that the United States was aware of their plans, Yamamoto and Nagumo would in all likelihood have deployed their submarines in advance of the rest of the fleet, probably in a screen between Midway and Hawaii. These subs would discover the U.S. fleet steaming to Midway, alerting the Imperial fleet. Instead of finding an unprepared Japanese fleet in the middle of rearming after their bombing run on Midway, the U.S. carriers would have run right into a prepared ambush, carried out by superior aircraft and experienced aircrews.

If the tables had turned, it is possible that the United States could have suffered as catastrophic a defeat at Midway as the Japanese did in reality. One logical conclusion is that Midway would have fallen to the Japanese; although heavily defended, the island would have been surrounded. With the U.S. carriers gone, the Japanese would have had aerial dominance, allowing Imperial warships and aircraft to bomb the defenders at will.

What next? In this hypothetical scenario, the U.S. Navy would have been left with only one carrier in the entire Pacific (the U.S.S.Saratoga, which had was being refitted in San Diego during the battle). Although the U.S. would be able to construct new carriers in time, eventually overwhelming the Imperial Navy, this would take time. According to Cook, no new U.S. carriers could be completed before the end of 1942, essentially giving the Japanese free reign in the Pacific for six months.

Here we come to the third-order counterfactuals. What is probable is that Washington would have disappointed Yamamoto. Although the Japanese retained the strategic initiative for the time being, there is probably little chance that the Americans would have been willing to negotiate with Tokyo after a Midway disaster. Japan probably would have continued its advance, for a while. A revived Operation FS seems like a probable outcome, with no U.S. carriers to oppose it. Attacks and raids against Australia, Alaska, and Ceylon (now Sri Lanka) are other possibilities.

However, there is another, frightening possibility. Both Cook andJohn Stephan of the University of Hawaii have argued that Yamamoto, along with several other Imperial naval officers, argued that after the occupation of Midway, an island-hopping campaign should be undertaken with the final goal being the conquest of Hawaii.  This would be a tall order in any case, with the Japanese Navy operating at the end of an extremely long supply line, but without a U.S. carrier force to oppose it, it is at least theoretically plausible. In any case, Hawaii would have been increasingly isolated.

How could the United States respond? Whether or not Hawaii could be occupied, defeating Japan would be a much more daunting task after a defeat at Midway. The United States would have had to build a new Pacific carrier fleet, almost from scratch, and start a potential island-hopping campaign much further east than the Solomon Islands. This could potentially have taken much longer than it actually did. In the absence of a U.S. carrier fleet, another alternative could be a determined U.S. advance via Alaska.

The wider possible implications are also important. If the United States had lost most of its carriers at Midway, would the allies have continued to pursue a “Europe First” policy, as they actually did? In the end, however, the war would in all likelihood have ended in a way familiar to our history books: with the atomic destruction of Japanese cities.Whether this would have persuaded the Japanese government to surrender or not is another matter.

Small and seemingly insignificant events can have huge implications. Although the Pacific War was a horrible, drawn-out conflict, a couple of code-breakers in Pearl Harbor might have prevented it from being even worse.