In 1964 he was diagnosed by a military doctor with an "abnormal personality" and "unfit for war and peace" ("untauglich für Krieg und Frieden") and was released from service.

[citation needed] In the German newspaper Die Zeit of 1977 Walraff formulates a sentence that is central to his work: “If I want to make myself the mouthpiece of the voiceless who have little to say even though they have a lot to say, that means to me that I am one of them, at least temporarily.

"[3] Wallraff first took up this kind of investigative journalism in 1969 when he published 13 unerwünschte Reportagen ("13 undesired reports") in which he described what he experienced when acting the parts of an alcoholic, a homeless person, and a worker in a chemicals factory.

Ganz unten ("Lowest of the Low") (1985) documented Wallraff's posing as a Turkish "Gastarbeiter", and the mistreatment he received in that role at the hands of employers, landlords and the German government.

In December 1996, Wallraff met with PKK leader Abdullah Öcalan at a Syrian training camp to discuss The Surahs of Kurdish dissident Selim Çürükkaya, who was threatened with death because of this book.

Wallraff was warmly received by Öcalan thanks to his role as the Turkish worker "Ali", but failed in getting the murder order overturned.

[8] In January 2003, Russia turned away Wallraff and two other Germans, the former labour minister for the CDU Norbert Blüm and Rupert Neudeck, head of the relief organisation Cap Anamur, as they tried to enter the country to work on a human rights article about Chechnya.

[11][12] His investigative methods have led to the creation of the Swedish verb wallraffa, meaning "to expose misconduct from the inside by assuming a role".

[13][14][15] Wallraff has been heavily criticised by those on the receiving end of his style of investigation, via attempts to frame his work as breaching privacy rights or revealing trade secrets.

Attempts were made on a number of occasions to legally prevent Wallraff's investigative methods, but his actions were regularly ruled constitutional by the courts.