When Lebedev abandoned the REOD and moved to America in 1936, Slonim continued his work. This was an especially controversial decision, as the REOD became exposed for its links with the Union for Repatriation and the NKVD. Slonim ultimately presented his resignation in July 1938. In June 1939, he met Tsvetaeva one final time in Paris, as she and Efron began their return trip to the Soviet Union. Slonim was still in Paris after the Nazi–Soviet Pact and before the Nazi invasion of France. Arrested for his contacts with the French communists, he was sent to a French concentration camp. By August 1941, he was in Spain, taking the SS "Navemar" from Seville to New York City. He completed the journey, despite the "Navemar"s "criminally inadequate" facilities, alongside friends Zosa Szajkowski and Mark Zborowski.