October 1942. Basilone, Morgan, Rodriguez, and their men patrol the jungles of Guadalcanal, engaging in deadly firefights with the enemy. Throughout, Basilone demonstrates vigorous leadership that endears him to his men. The arrival of an Army regiment provides Leckie, Basilone, and their comrades with the opportunity to pilfer a windfall of supplies. Soon after, there is a major Japanese naval bombardment, and the 1st Marine Division suffers heavy casualties. Col. Puller warns his men that the Japanese are mounting a night-time offensive to retake the airfield, and that the Seventh Marines will likely be right in their path. Thousands of Japanese attempt to break through the American line, but their effort fails.
Basilone displays extraordinary courage during the battle, risking his life to resupply his fellow machine gunners with ammunition and almost single-handedly holding back the enemy - despite suffering serious burns from moving his red-hot machine gun. By dawn, the carnage is revealed, but the hard-won victory comes at a grievous cost to Basilone when he discovers Rodriguez's dead body. Col. Puller tells Basilone he's recommending him for a medal for his actions.
Meanwhile back in Alabama, Sledge elatedly secures his father's permission to enlist in the Marines. His father, who treated soldiers wounded in the First World War, privately laments because he knows what his son is about to endure.
When the Marines are finally evacuated from Guadalcanal on the eve of Christmas, Leckie and his group are stunned to discover that the entire country has followed their campaign on this remote island, and he and his buddies are heroes.