Entering politics, Henning joined the
conservative German National People's Party (DNVP) and was elected to the
Reichstag in 1920.
Rathenau controversy Henning became notorious for an article of his that appeared in the June 1922 edition of
Konservative Monatsschrift. In the article, 'The Real Face of Rapallo Terror', Henning denounced
Walther Rathenau as an "international Jew" who had sullied German honour by not mentioning the murder of envoy Wilhelm Graf von Mirbach-Horff in
Moscow during the
Treaty of Rapallo negotiations. With Rathenau murdered at around the same time it appeared that rogue elements within the DNVP were endorsing political murder and so, under pressure from Chancellor
Joseph Wirth, the DNVP leadership expelled the
far right anti-Semitic wing, including Henning. In response Henning joined with Wulle and von Graefe in establishing the
German Völkisch Freedom Party (DVFP) as a rightist splinter group. Henning continued to represent this group (as well as the
National Socialist Freedom Movement, a joint list with the
Nazi Party active after the
Beer Hall Putsch) in the Reichstag until 1928. ==Later years==