Werner Haftmann has long been considered one of postwar Germany’s most important art historians. He wrote important texts that staked a claim for the art that the Nazis had labeled “degenerate,” and he advocated for a return to the educational principles of the Bauhaus movement. He was also influential in the development of Documenta and served as the founding director of Berlin’s Neue Nationalgalerie from 1967 to 1974. Now, new research points to evidence that Haftmann lied about being a member of the SA, the Nazi Party’s paramilitary wing.

The findings were published in an article for Hamburg-based weekly newspaper Die Ziet written by writer Karin Wieland and sociologist Heinz Bude, who is also the founding director of the Documenta Institute, a new organization that is conducting research into Documenta’s history.

“Probably no other art historian in the early Federal Republic was as influential as Werner Haftmann,” Bude and Wieland write in Die Ziet. “He had to offer a term for the art of the 20th century with which he opened his audience’s eyes to the power and intelligence of the works of art that were ostracized under National Socialism.”

Haftmann’s writings and theories were influential during the early editions of Documenta, the quinquennial contemporary art exhibition that was founded in 1955 in Kassel, Germany. The year before, Haftmann had published his seminal book Painting in the 20th Century, which proved key for Documenta’s founder, Arnold Bode, who invited Haftmann to serve as an adviser to the first three editions of the exhibition.

In November 1933, Adolf Hitler, who had become Reich Chancellor earlier that year, held an election that included a referendum on Germany’s membership in the League of Nations; 95 percent of voters called for Germany to withdraw from the League of Nations and 92 percent voted for the Nazi Party. Nine days before that election took place Haftmann joined the SA, according to Bude and Wieland’s research.

After World War II, as the country was going through its denazification process, Haftmann testified in 1946 that he had never officially been a member of either the Nazi Party or the SA and had only applied to be in both. “In both cases he lied,” Bude and Wieland write in Die Ziet.

Last year, art historians Julia Friedrich and Bernhard Fulda published findings concluding that Haftmann had in fact been a member of the Nazi Party, but could not be definitely say if he had been in the SA, the records for which were inconsistent prior to 1934. Now, Bude and Wieland have discovered evidence in the archives of Humboldt University of Berlin, where Haftmann was an art history student, that show a student card for 1934 in which Haftmann said he had been an SA member since the previous November.

Membership to both the Nazi Party and the SA were strictly controlled after May 1933, and Haftmann used a brief window in the fall of 1933 in which students could obtain membership in the SA to do just that. In order for people to become members of the Nazi Party, they would have to prove their staunch support for it in related organizations, like the SA. In June 1937, Haftmann applied for membership in the Nazi Party and was admitted a few months later, according to his membership card, which is held in Germany’s Federal Archives.

Bude and Wieland contend that Haftmann’s ideas undergird “the hidden curriculum of this museum of 100 days” that is Documenta, adding “In Kassel there is still no way around Haftmann.”