Guadalcanal was the first land battle in the Pacific War between USA and Japan. This film was released in the same year as the events. Sure, there is plenty of patriotism and propaganda, but for a Hollywood combat film made in the war years, this is relatively understated. It warns that Japan is a formidable enemy and victory for the US military will be hard won.
This isn't war as hell. It is a morale booster intended to reassure the homefront. It is narrated by the character of a war correspondent, adapted from a book by a journalist reporting back for a news service. It follows the US Marines for six months, from landing on the beaches to being relieved by the US army. The voice over contributes strategic and philosophical context.
The focus is on the ordinary soldiers, who are presented as classless and multi-ethnic. It's a vehicle for a range of fine ensemble performances. William Bendix stands out as a brave, determined but slightly dim GI Joe from Brooklyn, a role he would play a few times. These men are not really fighting for strategic gain or country, but for each other. And to survive.
The film has a practical message for the homefront: send mail, give blood and buy war bonds. It warns them of what the returning soldiers will have experienced. By rowing back on the heroics, the film feels even more moving because it is credible. It shows death and suffering and told their families, and people of the future, that their sacrifice was worthy of respect.