In 1945 under Operation Epsilon in "the big sweep" throughout Germany, Harteck was arrested by the allied British and American Armed Forces for suspicion of aiding the Nazis in their nuclear weapons program and he was incarcerated at Farm Hall, an English house fitted with covert electronic listening devices, for six months.

[1] From 1928 to 1933, Harteck was a staff scientist at the KWI für physikalische Chemie und Elektrochemie (KWIPC) (Kaiser Wilhelm Institute for Physical Chemistry and Elektrochemistry) located in Dahlem-Berlin, where he worked with Karl Friedrich Bonhoeffer on experiments on parahydrogen and orthohydrogen.

While at the KWIPC, he completed his habilitation in 1931 at the Humboldt University of Berlin[1] where he also supervised the dissertation of Karl-Hermann Geib who later developed the Girdler sulfide process.

In April 1939, along with his teaching assistant Wilhelm Groth, Harteck made contact with the Reichskriegsministerium (RKM, Reich Ministry of War) to alert them to the potential of military applications of nuclear chain reactions.

Under his supervision Wilhelm Groth conducted the last enrichment experiments with the ultracentrifuge in Celle, a small town 120 km south of Hamburg.

In late spring 1945, Harteck was arrested by the allied British and American Armed Forces and incarcerated at Farm Hall for six months under Operation Epsilon.