In a stunning, choreographed, ten-minute sequence photographed from medium and long-shot views with incredible tracking shots from the side, the troops sweep out across the pockmarked lunar-like landscape, littered with muddy gullies, bomb craters, bodies, debris, shell holes and barbed wire, as the barrage continues to roar. They follow Dax, pitifully blowing the whistle and waving a pistol in his hand, leading his men toward the enemy position. As the men run, stoop, stumble, and crawl during the attack, stumbling over the corpses of comrades, reactions to the disastrous attack are recorded on their faces. Men fall as German machine guns cut them down on all sides. Thousands of them are slaughtered in no man's land before they even reach the halfway point or beyond their own defenses. Dax continues to run on during the intense attack across the smoky landscape. The French wounded and dead pile up, and the air is filled with the wails and moans of defeated, agonized, injured voices. The German fortress is impregnable as expected.

Mireau, who is a spectator [of the brutal sport of war] with binoculars in the command post a safe distance away, is impatient and hysterical. He asks about the next attack wave, seeing that a whole company has not even left the trenches:

Miserable cowards, they're not advancing...they're still in the trenches!

Enraged and humiliated, Mireau calls for Captain Nichols to notify Captain Rousseau (John Stein), the battery commander, and order him to open fire on his own troops who are still in the trenches: "The troops are mutinying, refusing to advance!" Rousseau respectfully refuses the request twice. Knowing that he must have written proof of the insane command - to 'cover his own ass,' Captain Rousseau requires the order in writing: "Supposing you're killed. Then where will I be?" Mireau screams back, threatening him with a court martial:

You'll be in front of a firing squad tomorrow morning, that's where you'll be. Hand over your command and report yourself under arrest to my headquarters.

The battery commander still refuses, and eventually calm prevails.

Men are retreating back into the trenches, and many more men are still in the trenches. Dax has returned and he attempts to get the rest of the men into the field attack, pushing and yelling at them. He finds that Lieutenant Roget hasn't ordered his men to leave the trenches. Attempting to encourage his men to courageously follow him, Dax climbs up the trench ladder, only to be thrown back in by a French soldier's body that rolls toward him - a memorable moment. The cowardly Roget sums up: "It's impossible, sir. All the men are falling back."

The attack is a failure - and a disaster, with the men justifiably resorting to self-protection. But scar-faced Mireau is infuriated at their cowardice and unable to admit that the attack was ill-conceived. To consequently cover up his own disastrous complicity, he announces that he plans to assemble a general court-martial for three o'clock the next day to selectively punish the regiment for its cowardice:

If those little sweethearts won't face German bullets, they'll face French ones!

To vengefully trump up charges and hide the vanity, ambition, and incompetence of the officers in their tactical disaster, Dax is summoned to the chateau to make a final determination regarding the courtmartial with Mireau and Broulard. Dax is first commanded to order his regimental officers to pick ten men from each company (a total of one hundred men) to stand trial in the general court-martial, and "tried under penalty of death for cowardice." The overbearing Mireau is still frustrated that half of the men never left the trenches, vengefully believing they have skimmed milk in their veins instead of blood:

Dax: They're not cowards, so if some of them didn't leave the trenches, it must have been because it was impossible.
Mireau: They were ordered to attack. It was their duty to obey that order. We can't leave it up to the men to decide when an order is possible or not. If it was impossible, the only proof of that would be their dead bodies lying in the bottom of the trenches. They are scum, Colonel, the whole rotten regiment; a pack of sneaking, whining, tail-dragging curs.
Dax: Do you really believe that, sir?
Mireau: Yes, I do. That's exactly what I believe. And what's more, it's an incontestable fact.

A man with a moral conscience, Dax is stunned and sickened by the accusations, knowing that his men were pinned down under intense fire, and performing as heroically as possible. His trenches are soaked in blood, but he must listen to the crass bargaining going on for the lives of his men who are considered cowards:

Then why not shoot the entire regiment? I'm perfectly serious...If it's an example you want, then take me...One man will do as well as a hundred. The logical choice is the officer most responsible for the attack.

Broulard doesn't wish to consider this as a "question of officers." They haggle over the number to be selected to be brought to trial. Instead of selecting a hundred men, a dozen men, or ten men from each company, the number is whittled down to a token number. Three men, one in each company's first wave, are to be selected by each company commander. Craftily, Broulard opts out of attending the court-martial that afternoon, further distancing himself from the inevitable inhumane treatment of three accused scapegoats: "Oh, I won't be there, Paul...I think it best that you handle this matter on your own." Dax, previously complimented as a defense lawyer, is chosen to act as defense counsel.

Outside in the hallway with Broulard, Mireau stops one of his own officers, Captain Rousseau, his own battery commander (who disobeyed his orders) because some of his artillery shells supposedly fell short. Overhearing the accusation, Broulard feels the charge is "bad stuff. Demoralizes the men." But Mireau, jittery and anxious to hide the incident, explains why he is avoiding a court inquiry with the Captain and transferring him elsewhere:

In cases like this, shells falling short, I-I always try to avoid an inquiry. It gets around among the men and makes a bad impression. Now, shelving will be the best discipline for him in my opinion.

A few moments later, Mireau also confronts Dax and continues to press the matter. Mireau threatens to break and ruin him after the affair is over because of his lack of respect and loyalty:

Get off this fancy talk with me, do you understand? Colonel Broulard seemed to think you were funny. I don't. I want you to drop this affair...Colonel Dax, when this mess is cleaned up, I'll break you...I'll ruin you. And it'll be just what you deserve, showing such little loyalty to your commanding officer.

Dax meets with his three regimental commanders (one of whom is Lieutenant Roget) and tells each of them to choose a man from their company. Each individual will then be placed under arrest, and appear before a general courtmartial by three o'clock in the afternoon. "The charge is cowardice in the face of the enemy."

Before the trial, Dax visits all three selected men in their prison cell - Corporal Paris, Private Arnaud, and Private Ferol. All of them express how they resent what has happened to them and how they were chosen. Corporal Paris was chosen by the blackmailing Lieutenant Roget following the murder of Lejeune on patrol, because Paris knew that Roget was both a murderer and a coward. Arnaud was chosen by a random drawing of lots - and picked "purely by chance". Ferol was selected because his captain believed he was a "social undesirable." Dax explains to them that the reason for their selection is "immaterial. Whatever the reason, you're on trial for your lives." In Paris' case, he cautions: "You've got no witnesses. Besides, such charges against an officer would only antagonize the court." They must continue to act like brave soldiers:

Stick to the stories you've told me, and don't let the prosecutor shake you out of them. Now remember, you'll be soldiers in the presence of superior officers, so act like what you are - soldiers! - and brave ones at that...When you answer questions, look the judges in the eye, don't whine, plead, or make speeches. That's my job. Simple statements, short, but make them so they can be heard all over the room and try not to repeat yourselves. I'll do that for you when I sum up.

In taut and compelling scenes, the trial is held in the clean, gleaming, high-ceilinged ballroom of the chateau, with a checkerboard pattern on the marble floor - the trial is a strategic chess-match, of sorts. Footsteps and voices echo through the great hall, with its forty-foot high ceiling. It is a 'kangaroo court' farce from the very beginning, without the slightest pretense of fairness. The president of the court-martial, Colonel Judge (Peter Capell) does not read or record the official lengthy indictment of cowardice: "This is a general courtmartial and we shall therefore dispense with unnecessary formalities. These men are charged with cowardice in the face of the enemy and will be tried for that offense." When pressed by Dax, he argues that "the indictment is lengthy and there's no point in reading it," and then only summarizes the charges: "The indictment is that the accused showed cowardice in the face of the enemy during the attack on the Ant Hill."

The testimony portion of the trial is a hurried, one-sided, rigged farce led by prosecutor, Major Saint-Auban.

(1) the first defendant, whining Private Ferol, is quickly brow-beaten and made to admit that he retreated after advancing only part of the way across no man's land.

Saint-Auban: Did you advance?...How far did you advance?
Ferol: To about the middle of no man's land, sir.
Saint-Auban: Then what did you do?
Ferol: ...Well, I saw that me and Meyer, sir...
Saint-Auban: I didn't ask you what you saw. The court has no concern with your visual experiences...
Ferol: I went back, sir.
Saint-Auban: In other words, Private Ferol, you retreated.
Ferol: Yes, sir.

(2) the second defendant, Arnaud, quietly and intelligently explains his advance to his own side's wire as far as he could go "...'til I was ordered back to the trenches by Captain Renoir." After being asked, "Did you urge your fellow soldiers forward?", he further relates: "Most of them were dead or wounded before they got three steps beyond the trenches." Nevertheless, he is labeled a coward for not urging them on, even though none of the men in the company got beyond their side's wire. Dax emphasizes that he was "designated a coward simply and purely because you drew a slip of paper marked X." Although Arnaud had distinguished himself in the past in "some of the bloodiest battles of the war," his testimony is overruled when it is argued that it is accepted practice to choose one enlisted man by lot as an example, no matter how many citations of bravery a man has: "It's accepted practice in the French Army to pick examples by lot." Arnaud is on trial, it is argued, for his current cowardice, not for his former bravery: "Medals are no defense." It also cannot be proven that he reached the German lines, even though "no one in the entire regiment got anywhere near the German wire."

(3) the third defendant, Corporal Paris, argues that he was knocked unconscious as he left the trench, with a large cut on his head to prove it, but his defense is also dismissed.

Dax: Why didn't you leave the trenches?
Paris: Major Vignon was shot, and he fell back on top of me, sir, and knocked me cold.
Dax: And were you lying unconscious in the trenches during the entire attack?
Paris: Yes, sir.
Judge: Have you any witnesses to that?
Paris: No, sir. I guess everybody was too busy to notice me. There were so many others lying dead anyway.
Judge: But you have no witnesses?
Paris: No, sir. I only have a rather large cut on my head, sir.
Judge: That could have been self-inflicted later.

In a memorable sequence, during final arguments, the prosecutor delivers his summation speech to the judges, pacing back and forth, polished boots clicking on the floor:

And I submit that attack was a stain on the flag of France, a blot on the honor of every man, woman, and child in the French nation. It is to us that the sad, distressing, repellent duty falls, gentlemen. I ask this court to find the accused guilty...

Dax provides an eloquent rebuttal, pacing back and forth between the three prisoners and the three judges, while showing genuine concern for the accused:

There are times when I am ashamed to be a member of the human race and this is one such occasion...I protest against being prevented from introducing evidence that I consider vital to the defense, the prosecution presented no witnesses, there has never been a written indictment of charges made against the defendants, and lastly, I protest against the fact that no stenographic record of this trial has been kept. The attack yesterday morning was no stain on the honor of France, but this court-martial is such a stain...Gentlemen of the court, to find these men guilty will be a crime to haunt each of you to the day you die. I can't believe that the noblest impulse in man, his compassion for another, can be completely dead here. Therefore, I humbly beg you to show mercy to these men.

The head of the court announces that the hearing is closed, and deliberations are to occur ("the court will now retire to deliberate"), although it is already obvious what the inevitable verdict will be. There is no scene of the jury's final decision! A quick fade-cut is made to the firing squad preparing for the execution, where an announcement of the schedule and weapons is made by the commanding sergeant.