Battle of the Coral Sea
Historians H. P. Willmott, Jonathan Parshall, and Anthony Tully think Yamamoto made an error in deciding support the MO. Since Yamamoto thought the big battle with the Americans would be at Midway, he should not have sent fleet carriers to less important battle like MO. Japanese naval forces were weakened at both the Coral Sea and Midway battles, which allowed the Allies to defeat them.