Significance of several major battles of World War 2?

Operation Overlord / The Invasion of Normandy showed the Allied Forces and other nations that if you want to defeat an evil force like the Nazis you have to do it up big. They went into that battle/operation with 6000 ships, thousands of planes and they brought their own portable port to supply the troops. They did that up big too. They made their own gas and they brought in millions of tons of supplies and armament and vehicles. They planned and trained for two years. This worked.

The Doolittle Raid taught the allied forces they needed to believe they could do it even when things happen, like a Japanese fisherman seeing them when they were too far away from Japan. They took the risk and achieved a good bombing of Japan. Japan learned the US and other allies would attack Japan. They never realized how formidable the US was. They never thought their country would be nearly leveled or could be annihilated by the Russians and Americans and all the allies.