In the immediate aftermath of the Japanese attack on Pearl Harbor, Marine Sgt. John Basilone prepares to ship out and confront the enemy somewhere in the Pacific, while budding journalist Robert Leckie enlists in the Marine Corps. Eugene Sledge, unable to enlist because of a heart murmur, says farewell to his best friend, Sidney Phillips, who is about to leave for boot camp. Exactly eight months after Pearl Harbor, the 1st Marine Division, including Leckie and Phillips, lands on Guadalcanal in order to secure its strategically vital airfield and prepare for the inevitable counterattack.

Physically and mentally debilitated after the four-month ordeal on Guadalcanal, Leckie, Basilone and thousands of their comrades land in Melbourne, where they are greeted by adoring crowds and viewed as the saviors of Australia. While his buddies carouse, Leckie becomes deeply attached to an Australian woman and her first-generation Greek family. Meanwhile, Basilone is awarded the Medal of Honor and is asked to return home to help sell U.S. war bonds.