During 1941, as a war correspondent for Nazi Germany, Buchheim joined the crew of U-96 for a single patrol. His orders were to photograph and describe the U-boat in action for propaganda purposes. From his experiences, he wrote a short story, "Die Eichenlaubfahrt" (The Oak-Leaves Patrol) and a novel, Das Boot.
His trilogy U-Bootkrieg (U-Boat War), U-Bootfahrer (U-Boat Drivers), and Zu Tode Gesiegt (Victoried to Death), includes over 5000 snapshots taken during World War II. He is also the author of the novels Die Festung (The Fortress) and Der Abschied (The Parting).
Buchheim created the Buchheim Museum of Imagination, on the shore of Lake Starnberg, which containing an important collection of Expressionist paintings and graphics as well as curiosities ranging from nutcrackers and Thai shadow puppets to mannequins and carousel animals.