Midway 1942 Wargame

No, this is not about the venerable old classic board game Midway by Avalon Hill. This article is about the wargame run by the Imperial Japanese Navy in 1942 which had eerie hints of what was going to happen in the waters around Midway Island.

All internet images removed from this post, sorry.

The Covid-19 lockdown inspired some reading. The Conquest of New Spain by Bernal Diaz was followed by the similarly themed Conquest by Hugh Thomas. Then a 1,000 page opus about Harry Truman saw me back off. Maybe I’ll return to it in time. Instead I have begun reading Miracle at Midway by Gordon Prange. I knew some about the IJN wargame before but this gives greater detail.

A month before the battle the Imperial Japanese Navy wanted to have a rehearsal of sorts for the coming invasion of Midway and the exploitation that would follow the expected victory. Admiral Isoroku Yamamoto tasked his chief of staff, Rear Admiral Matome Ugaki with organizing a large table wargame of the looming operation. Ugaki had expressed doubts earlier about US planes hitting the Japanese aircraft carriers while the Japanese planes were striking the island. But he put these aside to run the wargame.  

During the game, the US planes from Midway attacked the carriers while the Japanese planes were striking the island. The umpire ruled that the US planes got 9 hits, sinking the fleet carriers Akagi and Kaga. Ugaki intervened, reducing the hits to 3, sinking only the Kaga and slightly damaging the Akagi. In the actual battle, US carrier planes sank 3 Japanese fleet carriers with planes refueling and rearming on their flight decks on the first strike. They got the remaining large carrier in a later strike, losing one US carrier and altering the naval balance of power in the Pacific for the rest of the war. Ugaki wasn’t done meddling. After the successful conclusion of the wargame invasion, the Japanese fleet moved towards New Caledonia and Fiji. Ugaki resurrected the sunken Kaga and added it to the Japanese fleet. He wasn't able to work such magic the next month when push came to shove.

This makes the wargame seem eerily prescient. A close look shows it got there by a series of errors. The wargame presumed the 9 hits were dealt out by the aircraft on Midway Island. It also presumed the attack was a strategic surprise though the Island garrison itself wasn’t caught flat-footed. It was assumed the US Navy would only know about the attack after Midway was hit. In the game the Japanese officer playing the US Navy declined to come out of Pearl Harbor to counter-attack, aware of how outnumbered he was.

There were a number of incorrect assumptions. First and foremost, the US Navy knew the attack was coming, Naval intelligence had broken enough of the Japanese naval code that with hard work and some good guesses they knew the target and time of attack. They were helped by the way the Japanese blabbed over the radio, in contrast to the complete silence maintained by the earlier Pearl Harbor strike. Second, most of the operative units of the US Navy were waiting northeast of Midway Island looking for a chance to ambush the Japanese. Aware of some of the disparity in surface combat ships, the US resolved to keep the fight strictly between planes and stay out of surface combat range. Finally, the Midway garrison had Marine Corps pilots stuck with badly obsolete “Brewster” fighters and “Vindicator” dive bombers. The leathernecks called the fighters “flying coffins” and the bombers “wind indicators”. All would fare poorly against the excellent Japanese Zero fighters. The Army Air Corps had a number of B-17 bombers on Midway, but they failed to score a single hit from high altitude against ships taking evasive action. Later in the war heavy bombers would make low level skip bombing attacks against shipping with more success, but the technique was waiting to be discovered. The Midway planes were valiant but ineffectual.

Ugaki’s meddling ensured that the game provided no useful warning to his navy. Overconfidence based on the wild run of victories the Japanese had chalked up in the 6 months since Pearl Harbor played a large part. Finally, fortune decided to smile on the US when their dive bombers came out of the clouds over the Japanese carriers, finding decks cluttered with planes, gasoline, bombs and torpedoes.