stylistic:tone
Guillaume affair

Around 1973, West German security organizations received information that one of Brandt's personal assistants, Günter Guillaume, was a spy for the East German intelligence services. Brandt was asked to continue working as usual, and he agreed to do so, even taking a private vacation with Guillaume. Guillaume was arrested on 24 April 1974, and many blamed Brandt for having a communist spy in his inner circle.

Brandt resigned from his position as chancellor on 6 May 1974, but he remained a member of the Bundestag and chairman of the Social Democrats until 1987.This espionage affair is widely considered to have been just the trigger for Brandt's resignation, not the fundamental cause. As Brandt himself later said, "I was exhausted, for reasons which had nothing to do with the affair going on at the time." Brandt was dogged by scandals about serial adultery, and reportedly also struggled with alcohol and depression. There was also the economic fallout on West Germany of the 1973 oil crisis, which may seem to have given enough stress to finish off Brandt as the Chancellor.

Guillaume had been an espionage agent for East Germany, who was supervised by Markus Wolf, the head of the Main Directorate for Reconnaissance (Hauptverwaltung Aufklärung or HVA—the foreign intelligence service) of the East German Ministry for State Security. Wolf stated after the reunification that the resignation of Brandt had never been intended, and that the planting and handling of Guillaume had been one of the biggest mistakes of the East German secret services.

Brandt was succeeded as the Chancellor of the Bundesrepublik by his fellow Social Democrat, Helmut Schmidt. For the rest of his life, Brandt remained suspicious that his fellow Social Democrat (and longtime rival) Herbert Wehner had been scheming for Brandt's downfall. However, there is scant evidence to corroborate this suspicion.