As a senior Communist Party of Germany member and Gulag survivor, which turned her into a staunch anti-communist, she wrote the famous memoir Under Two Dictators.

It begins with her arrest in Moscow during Joseph Stalin's Great Purge, followed by her imprisonment as a political prisoner in both the Soviet Gulag and the Nazi concentration camp system, after being handed over by the NKVD to the Gestapo during World War II.

[10] On 27 April 1937, while living at Moscow's Hotel Lux, Heinz Neumann was arrested as part of Joseph Stalin's Great Purge.

Buber-Neumann was unpopular with most of the women as Communist inmates, who were influential in the camp, disapproved her testifying to the hardships she had endured in the Soviet Union.

Seeking to avoid the advancing Russian troops, she made it to Hanover, Germany, where she sent a telegram to her daughters in Palestine.

At the urging of her friend Arthur Koestler, in this book she gave an account of her years in both Soviet prison and Nazi concentration camps.

[5] Die Gazette said of these works, "they shook up the post-war generation in West Germany because they reported for the first time and in great detail on the camps of the Soviet gulag.

[3] She joined the anti-communist Congress for Cultural Freedom with Arthur Koestler, Bertrand Russell, Karl Jaspers, Jacques Maritain, Raymond Aron, A. J. Ayer, Ignazio Silone, Nicola Chiaromonte, and Sidney Hook.

[3] In 1959, Arthur Koestler asked her to join him at his home in Alpbach to meet Whittaker Chambers and his wife Esther Shemitz while they were visiting Europe.

In 1976, she published Die erloschene Flamme: Schicksale meiner Zeit (The Extinct Flame: Fates of My Time), in which she argued that Nazism and Communism were in practice the same.

[3] Regarding Communism and Nazism, Buber-Neumann wrote: Between the misdeeds of Hitler and those of Stalin, in my opinion, there exists only a quantitative difference...

[7] Poet Adeline Baldacchino wrote: Margarete Buber-Neumann had the sad privilege to span the 20th century as the only person to have testified publicly in writing about the experience of both Soviet and Nazi camps.

[17][e]Historian Tony Judt held her among "the most interesting political writers, social commentators, or public moralists of the age" in a list that includes Émile Zola, Václav Havel, Karl Kraus, Alva Myrdal, and Sidney Hook.

[23] Judt wrote that she had written one of the best accounts by an ex-communist and listed her among Albert Camus, Ignazio Silone, Manès Sperber, Arthur Koestler, Jorge Semprún, Wolfgang Leonhard, and Claude Roy.

[23] Writer Camila Loew chose Buber-Neumann as with Ruth Klüger, Marguerite Duras, and Charlotte Delbo as "main witnesses" to "reflect on the relationship between history and literature, or between the materiality of pain (the experience of [the] body) and its representation in text.