Dictionary of Art HistoriansArchitectural historian of medieval architecture at the Herziana, Rome. Hahn was the son of Otto Hahn (1879-1968), a Nobel-prize-winning Chemist, and Edith Junghans (Hahn) (1887-1968), an artist. He attended the humanistic Arndt-Gymnasium entering Friedrich-Wilhelms-Universität Berlin in 1940 studying theater, German studies and philosophy. In 1942 he enlisted in the German army, commissioned as a lieutenant and fought on the eastern front as a Panzer (tank) leader. Heavily decorated, he was badly wounded in 1944 at Pietrow, requiring an arm amputation. While recovering, he met and later married his attending nurse, Ilse Pletz (1920-1960), wed in 1945. After the war, Hahn resumed his studies at the University of Tübingen and later University of Frankfurt am Main studying art history, archeology, philosophy and Italian philology. While at the Scuola Normale Superiore and the University in Pisa he became fascinated in medieval architecture. He returned to Frankfurt, writing a dissertation on Cistercian architecture under Harald Keller. After briefly volunteering at the Städelschen Kunstinstitut in Frankfurt he was appointed to the Bibliotheca Hertziana (Rome) in 1955 with a scholarship. While at the Hertziana another scholar, Heinrich M. Schwarz, was killed in an auto accident in 1957. Hahn assumed Schawrtz’ editing duties a Festschrift for Leo Bruhns, Franziskus Wolff Metternich and Ludwig Schudt. That same year Hahn’s magisterial Die frühe Kirchenbaukunst der Zisterzienser (Early Cistercian Church Architecture) appeared, notably positing, among other things the proportional scheme of Cistercian architecture. In 1959 he and his father were part of the first German delegation to visit Israel since the World War II, opening up what would later be formal diplomatic relations. While on a study trip in France, Hahn and his wife were killed at Mars-la-Tour (Lorraine) in an auto accident in 1960. The festschrift was left incomplete for a second time (ironically for the same reason as the first). Hahn’s doktorvater, Keller, was assigned to complete the volume. Hahn’s second book, Hohenstaufenburgen in Süditalien (South Italian Castles of the Hohenstaufen Era) appeared posthumously in 1961, edited by Gerda Soergel (b. 1920) (later Panofsky, who married Erwin Panofsky some years later).
Hahn’s reputation was established with his Cistercian church book where he theorized the “Laws” (his word) of Cisterican architectural proportion. Based on the first plan of the monastery at Eberbach and others, he stated a series of mathematical relationships that Cictercian builders employed extensively, if not rigorously.