Which 1942 battle is credited with turning the tide in the Pacific by breaking Japanese naval codes and sinking four carriers?

• A. Battle of Coral Sea
• B. Battle of Guadalcanal
• C. Battle of Midway
• D. Battle of Leyte Gulf

Answer: (C)

The big idea is how intelligence and decisive carrier warfare together can change a war’s momentum. At Midway in 1942, American codebreakers finally cracked Japanese naval codes (JN-25), revealing that a Japanese strike against Midway was planned and roughly when and where it would happen. This let the U.S. position its carriers and planes to ambush the Japanese fleet, inflicting a severe blow: four Japanese fleet carriers were sunk, dealing a crippling blow to their carrier strength for the rest of the war.

That combination—knowing the plan in advance and using it to bait and defeat the enemy with superior carrier power—makes Midway the turning point in the Pacific. By contrast, the Battle of the Coral Sea halted a Japanese invasion but did not erase their carrier threat or deliver the same strategic collapse. Guadalcanal checked Japanese expansion and began a long, costly campaign, but it did not deliver the decisive carrier losses Midway did. Leyte Gulf happened later and shifted momentum even further, but years after the Midway turning point.