After the Marine Brigade Ehrhardt was disbanded, some of the soldiers were incorporated into the regular Reichswehr. In the fall of 1920, the rest of the unit formed the Organisation Consul, an underground right-wing organization that used assassinations to try to provoke a coup from the left so that it could then offer its support to the Reich government in fighting it. Ehrhardt hoped in that way to gain enough influence to be able to change the constitution to make Germany a dictatorship.
Members of the Organisation Consul planned and carried out the assassinations of the former Minister of Finance Matthias Erzberger (26 August 1921) and Foreign Minister Walther Rathenau (24 June 1922) and the attempted assassination of former Minister President Philipp Scheidemann (4 June 1922). The "Consul" in the Organisation Consul was Ehrhardt himself, who had an aide-de-camp and his own staff. Together, they controlled all aspects of the tightly run military organization.
In the aftermath of Erzberger's murder, Ehrhardt fled to Hungary to escape imminent arrest. In the absence of its leader, the Organisation Consul disintegrated and was banned by the Act for the Protection of the Republic (Gesetz zum Schutze der Republik) on 21 July 1922. Otto Pittinger, the leader of the moderate-right Bund Bayern und Reich (League for Bavaria and Reich) seized the opportunity and tried to win over and de-radicalize the Ehrhardt group, giving rise to the Neudeutsche Bund (New German League), which tried to unite the former fighters of the Ehrhardt Brigade. Ehrhardt himself, who had returned from exile, joined the movement but was arrested in November 1922.
From prison in 1923, Ehrhardt instructed Captain Lieutenant Eberhard Kautter to reorganise the New German League. It then became the Viking League (Bund Wiking), which operated throughout the Reich, and according to its own figures, there were about 10,000 members. In July 1923, Ehrhardt escaped from prison and fled to Switzerland before returning to Munich on 29 September. He supported the conservative group around Bavarian State Commissioner Gustav Ritter von Kahr, who wanted a right-wing dictatorship to replace the Weimar Republic, but not one under Adolf Hitler's leadership. Ehrhardt then prepared himself to oppose the Hitler-Ludendorff Beer Hall Putsch on 8/9 November 1923. He assembled his troops – consisting mainly of formations of the Viking League – in Upper Franconia and was ready to march against Hitler, but by then the putsch had already failed in Munich.
Ehrhardt had had early contact with Hitler and his National Socialist movement. When Ernst Röhm was looking for experienced men to lead his Sturmabteilung (SA), he turned to Ehrhardt. At first, Ehrhardt wanted nothing to do with Hitler and said, "Good God, what does the idiot want now?" He eventually let Röhm persuade him and transferred several of his men to Hitler. Hans Ulrich Klintzsch, a lieutenant in the Organisation Consul, became head of the SA, and Alfred Hoffmann, an Ehrhardt man, became chief of staff. But just two months later, Ehrhardt ended his association with Hitler and the SA and withdrew some of his men.
After the 1923 Beer Hall Putsch, Ehrhardt lost his standing with the radical right-wing forces in Munich. He was considered a traitor because he had opposed Hitler. As a result, the Viking League also lost importance. In April 1924, Ehrhardt again fled to Austria to evade prosecution by the German Reich. He returned in October 1926 after an amnesty by the new Reich president, Paul von Hindenburg. In the meantime, the Viking League had lost so much of its importance that Ehrhardt felt compelled to enter into negotiations with Der Stahlhelm, a right-wing veterans group, into which the League was to be absorbed. The negotiations failed, and on 27 April 1928, the Viking League was dissolved.
Ehrhardt later contested for dominance over the revolutionary right against Hitler, but he was unsuccessful, with many of Ehrhardt's men joining the Nazi Party. The Gefolgschaft (fellowship) founded in 1931 by Ehrhardt and ex-Marine Brigade Ehrhardt member Hartmut Plaas brought together 2,000 of his followers along with disappointed National Socialists and Communists who wanted to prevent Hitler from taking power and who above all denounced the demagoguery of the Nazis. Ehrhardt became involved in attempts to destabilise the Nazis and worked behind the scenes to forge an alliance between dissident SA leader Walter Stennes and Black Front leader Otto Strasser. Ultimately the initiative was not a success. Strasser abandoned Stennes when he learned that Ehrhardt was behind the plan to link the two leaders.
Some of Ehrhardt's followers later became involved with the resistance to Nazism. They included journalist Friedrich Wilhelm Heinz, press officer Herbert von Bose and editor Hartmut Plaas. The historian Armin Mohler pointed to the connections that leading members of the military resistance, such as Admiral Wilhelm Canaris and General Hans Oster, had to Ehrhardt.
On 28 June 1933, the newspaper Westhavelländische Tageszeitung reported that the SS had announced that "Captain Ehrhardt has declared his allegiance to the Nazi Party". He had "personally joined the party" and "had subordinated himself along with his military unit, the Brigade Ehrhardt, to the Reichsführer of the SS." The Ehrhardt Brigade stayed in the SS only a short time. After Ehrhardt was promoted to SS-Gruppenführer in the second half of January 1934, the association was dissolved by SS-Reichsführer Heinrich Himmler on 1 February 1934.
Ehrhardt's life was also in danger. Along with many other former opponents of Hitler, he was to be murdered during the Nazi internal purge known as the Night of the Long Knives in June/July 1934. He fled in time, first from the SS to a forest near his estate, then to Switzerland. In 1936, he went to Austria with his family and ran the manorial estate Schloss Brunn am Walde near Lichtenau im Waldviertel. Until his death in 1971, he lived as a farmer and was no longer politically or militarily active.
