Flying didn’t come easy to Zenos Ramsey Miller. While training with the 27th Aero Squadron in France in 1918, Miller kept a daily journal. “In the afternoon on my fifth-spiral I pancake on my landing and crack my left lower wing on a cheval debois,” he wrote on April 12. Five days later, he noted gloomily, “Cracked wing and broken tail skid added to my record of casualties.” Two days later, Miller passed the acrobatics field “and was laughed at.”

But he persevered. In May Miller was sent to the Western Front, at Epiez Aerodrome, and he and his squadron began patrolling regularly in Nieuport 28s. Three patrols went up each day, with the purpose of barring enemy observation photographers from entering allied airspace.

On July 16, Miller shot down two enemy observation balloons—the second while in a dogfight with three Fokkers. Three days later, the patrol encountered seven Fokker D.VIIs; Miller scored his third victory. On July 20, the five-man patrol fought seven enemy aircraft; Miller shot down two of them, making him an ace.

But that dogfight took him out of the war: He and two others were shot down. Lieutenant John MacArthur—Miller’s closest friend in the squadron—was killed in action. Lieutenant Fred Norton died of his injuries a few days later. Miller was taken prisoner and sent first to Trausnitz Castle (near the Bavarian town of Landshut), then to Villingen, near the Swiss border.

While a POW, Miller kept a diary, which, along with his 1918 datebook, is now in the collection of the National Air and Space Museum. The diary is an exceptional historic document: It contains entries by 124 POWs, including their names, addresses, and circumstances of capture. The book also includes descriptions and drawings of prison camp life.

Villingen, the former barracks of the 3rd Battalion, 169th Infantry Regiment, was first used to house captured Russian officers. But by 1918, the United States demanded that Germany combine all American POWs in two camps, one for enlisted men, the other for officers; by June, American officers began arriving at Villingen.

Compared to some prisoner of war camps, Villingen was luxurious: It offered such comforts as a music room, two canteens, a volleyball court, and a softball diamond. Because they were officers, the prisoners were allowed to walk outside the camp while accompanied by a German officer. (The men had to sign a pledge that they wouldn’t try to escape.)

Villingen, like other officers’ prison camps, allowed a local photographer to enter the camp and take souvenir portraits, which were sold to the prisoners. Miller’s diary includes dozens of photographs of prisoners, individually and in groups.

The November 1918 Armistice freed Miller and his fellow POWs. December 25 found him in Paris, heading for home. “Had lunch with [fellow POWs] Ed Klingman & Bradfield who are on leave from Tours,” he wrote in the final entry in his datebook. “Was glad not to have to spend Xmas day alone. Saw Clark as well he was all dolled up and had a date with some little French miss who turned him down. Poor boy oh!”

By July 1922, Miller had returned to Boston and was enrolled in Harvard medical school. He, his brother Ralph, and Clarence Gamble decided to undertake a transcontinental flight to California. On the first leg of the trip, their Savoia-Marchetti went into a spin over Framingham, Massachusetts and crashed. Ralph Miller and Clarence Gamble were severely injured; Zenos Miller was killed. He was 24 years old.