During 1930–1933, he served as editor, publishing director and later chairman of the independent radio-federal employees and the paramilitary wing of the Communist Party.

There he worked as a journalist, as an editor of Tribunal, and organized for the International Red Aid in Spain relief efforts for the Victims of the Asturian miners' uprising.

According to information later received by British Intelligence, Kahle was alleged to have been one of the leading spymasters for the NKVD, the Soviet political police, in the Second Spanish Republic.

He was a founding member of the Free Germany Movement, which was believed by MI5, the British domestic counterintelligence service, to be a front for recruiting anti-Nazi refugees into a Soviet NKGB spy ring.

For this very reason, in fact, intercepting a wartime letter to Kahle from Eric Hobsbawm led MI5 to start a file on the latter.