Barthas describes lice and exploding 105-millimeter shells in the same matter-of-fact voice, although the shells do cause him to raise an eyebrow from time to time. During a heavy bombardment, a trench mate disappears under a mountain of earth. Before Barthas can dig him out, a second shell falls, displacing the dirt pile and restoring the status quo, like a film sequence run in reverse. The bewildered soldier suffers nothing worse than a crack in his clay pipe.

Barthas has a keen interest in the power struggles between top officers and the lower echelons, which are more complicated than one might think. It was not unusual to see spirited resistance to orders from on high. Enlisted men connived to thwart impossible commands, and midlevel commanders occasionally refused to send their men into impossible situations. Barthas himself loses a stripe by refusing to obey a captain’s orders to have two men dig a trench within machine-gun range of the Germans.

Pushed to the limit, French soldiers sometimes turned on their superiors. At Verdun, Barthas was making his way to the rear after being relieved when a young lieutenant, waving a gun in his face, ordered him to halt. “Outraged by this highly impolite way of stopping people,” Barthas writes, “I hoisted my Lebel rifle and replied to him, ‘You’ve got your revolver, I’ve got my rifle, so what do you want to do now?’ ” The lieutenant backs off.

Through tacit collaboration, the men on the front lines subvert the military code. French and Germans work out unspoken truces so that both sides can carry out work details, rescue the wounded or, at forward observation posts, fraternize.

When a corporal in Barthas’s company is badly wounded while rummaging through the pockets of the newly dead, a common nighttime activity on the front lines, the company captain pretends that he suffered his wound in the line of duty when a general makes inquiries. Bamboozled, the general says, “He will be commended, and will get the Croix de Guerre and the Médaille Militaire.” This tickles Barthas, who writes, “And that’s how Corporal Cathala became a hero.”

Any kick against authority pleased Barthas, up to and including surrender, an increasingly common dodge in the final stages of the war. “ ‘What cowards!’ say the patriots in the rear,” he writes. “But if all the soldiers, on both sides, had done the same thing, wouldn’t that have been sublime? The generals would have had to fight each other. Poincaré could have gone a couple of rounds in the boxing ring with the Kaiser. That would have been hilarious.”