Costa-Gavras, who is still making films at 86, was just a beginner when he made Un homme de trop (a.k.a. Shock Troops) in 1967, and arguably wouldn't hit his true stride until he made the Oscar-winning Z a couple of years later. The '67 movie, a French Resistance drama produced by James Bond mogul Harry Saltzman, was a big-budget flop. But it's also a genuine unknown masterpiece.
Speculating as to why the film wasn't a hit, the director supposed that maybe there was "too much action." Action, he said, is easy to do. Well, not for most filmmakers, not the way he does it. The movie is simply incredible—the most headlong film I can think of outside of Mad Max: Fury Road. True, there isn't quite as much fighting as all that—it isn't a single chase one way followed by another chase going back (see also Keaton's The General). But even when nobody's firing a machine gun or lobbing a grenade (or balancing a grenade in a glass atop a door as a death trap for incoming Nazis), the large cast is delivering their dialogue rat-a-tat fashion is fast-cut, highly mobile scenes in which classic technique (dollies and cranes) alternates with nouvelle vague innovation (zooms, trombone shots, freeze-frames).
The cast is crowded with actors you might sort of know, including Costa-Gavras favorites Bruno Cremer, Jean-Claude Brialy, and Jacques Perrin, but also Claude Brasseur and Charles Vanel and Pierre Clementi—the list goes on. And on. You need a lot of faces to represent a fighting unit, especially one that comes to have such a high mortality rate.
Narrative: the Maquis (rural French resistance) bust a dozen condemned men out of prison. Problem is, there's unexpectedly a thirteenth man. A spy? This looks like being a really exciting, high stakes whodunnit kind of thing, except that five minutes after the mystery is established, Michel Piccoli steps forward and says, "I'm the one you want. I'm the one who doesn't belong."
And yes, this film has the detective from Diabolik and the detective from Diaboliques.
Safest thing would be to kill him. He's "condemned by circumstance."
The film then generates much of its considerable tension from the heroes' failure to do away with this pleasant-seeming but odd and uncertain character. Will he betray them? Will they execute him, then find out he's innocent? (This has, apparently, happened before.) Meanwhile, they go from mission to mission, or are chased or besieged, in a series of violent, nail-biting, explosive, gigantic set-pieces. There's too much action, yes, but there's too much everything, in a film that has its own poetic and intellectual take on the cinema of excess, of spectacle, of melodrama and action.
These men, in between bouts of strenuous combat, recite improvised erotic poetry. So it's a very French action film. And this is most vividly seen in Piccoli's character, a central enigma who perplexes all who come in contact with him. Is he a pacifist or a turncoat, a harmless oddball or an enemy within? This kind of uncertainty is only acceptable in commercial cinema if it's clearly resolved, and Costa-Gavras isn't interested in that kind of tidiness. So the ending is calculated to frustrate the literal-minded. But even that is delivered with a staggering helicopter shot (there are quite a few of those) so that the unknowable and irrational aspects of the film are put over with blockbuster enthusiasm. And both Beckett and Camus were in the Resistance, and it influenced their work, so it's not like those two tones, the internal-absurdist and the epic, don't belong together.
Costa-Gavras might be right that the film's tremendous forward momentum and very modern tendency to burst out with an action sequence every ten minutes might get in the way of more meditative concerns. And the movie can't help but play into the then-popular mass delusion that all of France was in the Resistance (the director made the darker, more cynical and less gung-ho Section spéciale, about judicial collaboration with the Nazis, in 1975). But a lot of his punchiest cinematic effects come in otherwise quiet scenes, and have nothing to do with blasting tanks with bazookas, as enjoyable as that may be. When a young fighter dies from a bullet wound, the leader who stays with him (Cremer) is filmed with alternating (and slightly jerky) track-zooms, tromboning the interior space in distortions that evoke both the feverish state of the dying man, and the inner tension of the one who will live, while the amplified sound of chopping wood reverberating outside assumes the quality of a slurred heartbeat.