These guys went to every island in WWII. The Japanese were numerous and motivated like Hell's train. But the Marines landed on the beaches and while under a blanket of machine guns, artillery, and grenades... they moved on.
Iwo Jima really showed the courage of the Marines, they dove on grenades and ran through minefields, they took what it takes.
One Marine was charged by a Japanese Officer with a sword. While the sword was brought down upon the soldier, he grabed the blade and with a blooding hand, took that sword and stabbed the Jap Officer.
There are countless stories of bravery with the USMC but in reality all soldiers are tough (even the French ).