Wallach founded the (Wallach House), a specialist supplier of tracht and folk art, which became well-known outside the borders of Germany. In Austria, the wearing of folk costume was promoted by Viktor von Geramb (1884–1958), professor of folk culture at the universities of Graz and Vienna. He saw folk costume as a means of rejuvenating Austrian identity after the collapse of the Austro-Hungarian monarchy during the First World War. Von Geramb was critical of the tracht associations for insisting rigidly on the historic designs, which were treated as a uniform of the association. He argued that, for folk costume to be a living tradition, it needed to express the individuality of the wearer; thus designs and materials needed to be adapted to contemporary culture and technology. Accordingly, he worked with commercial firms on finding material and designs that would allow the production of folk costume in large quantities. Consequently, Alpine tracht gained in general popularity and even spread to eastern Austria, where it had not been part of the traditional clothing culture. The dirndl was increasingly perceived as the Austrian national dress. In 1930, the Wallach brothers supplied the stage costumes for the operetta The White Horse Inn (). The romantic comedy presented an idyllic picture of the Austrian Alps and had long runs in cities like Berlin, Vienna, Munich, London, Paris and New York. Inspired by the lively innkeeper heroine, the dirndl became an international fashion phenomenon, always with an apron and usually with deep décolletage. This widespread adoption was helped along by a general 1930s trend to a silhouette which matched the folk costume: full skirts, higher hemlines, broader shoulders and tailored waists. The dirndl was also promoted through the Trapp Family Singers, who wore dirndls during their performance at the Salzburg Festival (1936), and later on their worldwide tours. In addition, the film Heidi, with Shirley Temple in the lead role, became a hit in 1937. By that year, the dirndl was considered a 'must' in the wardrobe of every fashionable American woman. Appropriation by the Nazis (1930s–1945) German traditional costume, including the dirndl, was instrumentalized by the Nazis as a symbol of pan-German identity in the countries under Nazi rule (Germany from 1933, Austria from 1938). The dirndl was used to promote the Nazi ideal of the German woman as hard-working and fertile. An example is a propaganda photo released by the (Nazi Party) Office of