The movie is set in the war-time Vietnam. As widely known, the main plot follows that of the Heart of Darkness by Joseph Conrad. In my opinion, this is a mistake. Heart of Darkness was not great for its main plot. It was great for the confrontation with the unknown. The unknown was not Kurtz, but Africa. The river, the forest and its people looking at the protagonist with a vengeful aspect.
Sure enough, I'm certain that there were plenty of aspects, vengeful and worse, in Vietnam, but that misses the point. The inscrutable intention in the original is well-known in the case of Vietnam. It was how they were getting their weapons and where their traps lied that the G.I.s didn't know. The intention was fully known - they wanted to kill them.
The inscrutability of Africa was what made Heart of Darkness so fearful. Not knowing where you stand against what could be a friend or a foe, or simply an animal. Much like being in a dark cave, it fuels the irrational and insane fear. Heart of Darkness was named so, and not Heart of Horror for a reason.
What about other aspects of the film? There's the political side of it, of course. As much as it tries to stay clear of politics, one cannot avoid making political statements about Vietnam when talking about the war. There are hints, like mowing down of the innocent boat, napalm bombing of the village for surfing, accounts of the Vietcongs cutting off children's arms, and so on. Both sides are cruel, but one side is so in order to win the war, the other is simply fucking around.
That leads to the nice bits. Interesting depiction of the madness of war. I'm not saying the madness of the war, since the madness is globally applicable to all wars. One needs to look only as far as the Second World War and the venerable Joseph Heller's Catch-22 for that.
Indeed, the film is teeming with the madness of war - and by extension, the madness of humans, madness of everyday, the madness that is so obvious once the observer is not committing the act.
