What did the leaders of the US learn about the japanese after the battles at iwo jima and Okinawa

the Japanese used the island as defences and would be relentless

Explanation:

At the battle of Iwo Jima and Okinawa the japs built into the island and concealed their weapons and soldiers in the island. Their island hopping would gradually slow down. they had to step up their attacks and they started using flamethrower tanks