Born in Bern, the businessman Hermann Rupf was an avid collector of modern art. In 1907, he was Daniel Henry Kahnweiler’s first client at his Gallery in Paris. This catalogue contains previously unpublished archival material from the years 1933 to 1945, when Rupf and Kahnweiler continued their correspondence despite adverse circumstances; from 1940 onwards, their exchanges took place “in the shadow of the crematoria,” as Kahnweiler later put it. Supplementary essays offer context to their lengthy correspondence, shed light on art dealings after 1933 and Kahnweiler’s work in Paris, and pay tribute to his lifelong friendship with Rupf, whose collection is nowin the Kunstmuseum Bern.