The film opens with a question: “Why does nature contend with itself?”. It shows a crocodile, a killing machine. Later, as men prove more deadly than crocodiles, it shows a bird, its wing shattered by gunfire, pulling itself along the ground. In a way the film is not about war at all, but simply about the way in which all living beings are founded on the necessity of killing one another (and eating each other, either literally or figuratively).
The film opens with an idyll on a Pacific island. Two soldiers have gone AWOL and live blissfully with tribal people who exist in a pre-lapsarian state, eating the fruit that falls from the trees and the fish that leap from the seas, and smiling contentedly at the bounty of Eden. This is, the movie implies, a society that reflects man’s best nature. But reality interrupts when the two soldiers are captured and returned to their Army company for the assault on a crucial hill on Guadalcanal.
During the battle scenes, there will be flashbacks to the island idyll – and other flashbacks as a soldier remembers his love for his wife. […] The soldiers are not well-developed as individual characters. Covered in grime and blood, they look much alike, and we strain to hear their names, barked out mostly in one syllable (Welsh, Fife, Tall, Witt, Gaff, Bosche, Bell, Keck, Staros). Sometimes during an action we are not sure who we are watching, and have to piece it together afterward. I am sure battle is like that, but I’m not sure that was Malick’s point: I think he was just not much interested in the destinies and personalities of individual characters.
[…] The battle scenes themselves are masterful, in creating a sense of the geography of a particular hill, the way it is defended by Japanese bunkers, the ways in which the American soldiers attempt to take it. The camera crouches low in the grass, and as Malick focuses on locusts or blades of grass, we are reminded that a battle like this must have taken place with the soldiers’ eyes inches from the ground. The Japanese throughout are totally depersonalized (in one crucial scene, their language is not even translated with subtitles); they aren’t seen as enemies so much as necessary antagonists – an expression of nature’s compulsion to ‘contend with itself’.

Roger Ebert, “Chicago Sun-Times”, 8 gennaio 1999