In January 1918, Petroff and Gellrich were repatriated to the
Soviet Union alongside
Georgy Chicherin, the British government acceding to a request by
Trotsky; Petroff was made Vice-Commissar for Foreign Affairs, taking over from Zalkind. He subsequently served as Chairman of the Foreign Relations Committee, and Chairman of the Political Section of the Supreme Military Inspection of the Red Army. Although barred from visiting the UK, he remained in contact with Maclean, and also
Tom Quelch and
James Clunie. In 1921, he was sent to Germany, to support the communist party there. He was sympathetic to Trotsky's
Left Opposition, and resigned from the
Bolshevik Party in 1925, but remained active in the German communist movement until the Nazi rise to power. Petroff and Gellrich fled to Britain in 1933, where he worked as a journalist, principally for overseas newspapers. Given his opposition to
Stalin, he faced hostility from the
Communist Party of Great Britain, and instead joined the
Labour Party, writing extensively for its journal,
Labour. In 1934 he and his wife wrote
The Secret of Hitler`s Victory: The Causes of the Breakdown of the German Republic published in hardback by the
Hogarth Press. With the onset of
World War II, his work dried up, but he remained in London until his death, eight years later. ==References==