A tip of the hat for the internet. I figured somewhere I would find a photo of Quiqui, the black and white dog, who was among the survivors of the Battle of Fort Vaux. Voila!
The caption reads, "In the hell of the Great War, Quiqui has been the sole joy of Commandant Raynal who shared all his sufferings with him."
The internet also brought me excerpts from Commandant Raynal's journal. There I found more of Quiqui's story.
While organizing the defense of Fort Vaux, Commandant Raynal had arranged for a telephone, but when the team arrived, he was bewildered to discover that his telegraph team consisted of two men and a dog. The telegraph operators had been killed. The sapper, Trayler, convinced Raynal to keep his dog (a young crossbred cocker spaniel) because "He is a child of the troop! He was born in the month of March at Verdun and has three months of service!"
The dog was named "Marquis" because his mother, dead on the battlefield, had been named "Princess," but the sapper added that "if the name Marquis offends you, we have nicknamed him "Quiqui."
Quiqui was a very good dog. According to Commandant Raynal journal entry for May 31 "he had all the qualities that his foster father had claimed for him; he knew when to be quiet, he was very clean and nothing frightened him. From this point of view, he was a true poilu. At the start of the siege, each German grenade which detonated among us made him pounce and dash to the place where the grenade had fallen...As there was never anything to pick up, and he always returned empty-handed, he quickly gave up moving quickly and waited quietly sitting on his haunches for the bombardment to stop."
During the battle, on June 4: "Quiqui takes part in the battle; it is his custom now. He is almost a Grognard. Everything interests him, nothing worries him. He is naturally brave, like his mother dead on the battlefield. He rushes right into the corridors where grenades detonated; the combat which covers him in shadow and smoke, this combat where he no longer sees his friends, where he hears only the explosions, the cries of fury and distress, none of this holds him longer than an instant. Quickly he runs to the left corridor where machine guns crackle in the bunkers. Here air and light enter through huge cracks, death also, alas...He regards all, sees all, and seems to be taking part."
Quiqui stayed with Raynal and the sapper Trayler during their nearly three years as prisoners of war, living a good life: "My brave Quiqui has won the affection of all the captives. The English officers spoil him, corrupt him. They call him to every chamber, they stuff him with sweets, with cake. He is there when anyone opens a package, and he it is who is served first."
When the war ended, Raynal and Quiqui returned to France. ("That's it, my brave Quiqui! Now for France and liberty!") A good dog. A lucky dog, actually.