Snow mercy: Andy Serkis is in there somewhere. Twentieth Century Fox

I don’t know when it happened, but it happened. Somehow, while we were worrying about superheroes and star destroyers and hot rods and whether Captain America could beat up Superman or whatever, the goddamned Planet of the Apes movies became the most vital and resonant big-budget film series in the contemporary movie firmament. And they did it with the most confrontational of high concepts: Humans suck, and now the apes are the good guys.

To be fair, the films didn’t initially state that outright; they’ve steadily built to that idea. But elements were there right from the beginning. The Simian flu might be killing humans and making apes hyper-intelligent, but what’s really undone us across these three films has been our selfishness, cruelty, and nihilistic propensity to destroy that which we claim we want to save. This new film picks up a couple of years after 2014’s Dawn of the Planet of the Apes; that ended with all-out war being declared between the ascendant apes and the declining remnants of the human race, just ten years after the events of 2011’s Rise of the Planet of the Apes. Now, the tribe of apes led by Caesar (Andy Serkis) is hoping to flee to safety, behind a mountain range and across a desert beyond which, they believe, humanity will not follow them.

But of course, the humans won’t stop their pursuit. Sometimes, they come in small, heavily armed invading armies, using turncoat apes as slaves and scouts. Sometimes, they come in quiet raiding parties. One of this film’s most striking achievements — especially in its first half — is making us fear even the very silhouette of a human being. The men in this movie might as well be the xenomorphs from Aliens: strange, unspeakable beasts uncurling out of the shadows like demons from your worst nightmare.

Leading the humans is a messianic Colonel (Woody Harrelson), who inspires a kind of mindless devotion from his soldiers. I’m not sure if the Colonel has a name, but I’m gonna call him Kurtz, because he’s clearly channeling Marlon Brando’s portrayal of that character from Apocalypse Now, which itself was based on Joseph Conrad’s Heart of Darkness. (By the way, this is the second angry ape movie this year to reference Francis Ford Coppola’s film; what’s up with that?) Harrelson finds ways to bring shading to this monster. The humans themselves are grappling with a mutation of the Simian flu, which has begun to take speech and intelligence from many of those survivors who were once immune to its effects, and the cruel acts by “Kurtz” are as much a death rattle for his race as anything else.

Meanwhile, Caesar himself is also wrestling with his darker side, represented here by his visions of Koba (Toby Kebbell), the bitter, bellicose bonobo who in Dawn of the Planet of the Apes helped engineer the escalating enmity between apes and men. Across these films, Caesar’s rage and vengeance have always fought with his capacity for compassion, but in death, Koba has become the devil on Caesar’s shoulder — a temptation as well as a warning sign. There is no similar conflict among the men, it seems: In the intervening years, they have become a grunting, faceless, well-disciplined horde, in thrall to the preening, godlike bluster of the Colonel.

There’s something weirdly cathartic about the spectacle of humanity reduced to an animalistic throng. And it gives the film a disturbing, powerful kick. Of course, people are often capable of great evil; we don’t need the movies to tell us that. But the mindless, tribal destructiveness on display in this film is not some outside, unfamiliar force. These aren’t zombies. We recognize this impulse, this willingness to embrace raw hatred and give ourselves over to leaders who focus and cultivate our rage. These days, we know it all too well.

These last two Apes films were directed by Matt Reeves, who previously distinguished himself with the bleak, beautiful teen vampire drama Let Me In, a superior remake of the hit Swedish thriller Let the Right One In. This new one has all the reliable virtues of a well-made studio blockbuster: The effects are incredible, the action is exciting, the music is great, and Andy Serkis, once again embodying a nonhuman character through motion-capture technology, remains terrific.

But there’s something more here: Reeves likes his stuff dark — visually, thematically, narratively — and now he’s plunged us headlong into the gloom. War for the Planet of the Apes is certainly the most melancholy tentpole since…well, since Dawn of the Planet of the Apes. The subject matter may well lend itself to melodrama and spectacle, and while Reeves never skimps on suspense or emotion or epic imagery, he also understands the power of restraint, of quiet. The apes usually speak in sign language. The humans barely speak at all — those that can don’t really have anything worth saying. Meanwhile, the grim settings and mood — thick forests and desolate valleys and pitch-black caves — enhance the imperative for survival at all costs. The picture pulls us as viewers into an atmosphere so oppressive that it leaves no room for morality; we’re too caught up in the characters’ struggle for survival to worry about anything else. To put it another way: This movie is a dangerous place to be.