Steinbeck's contacts with leftist authors, journalists, and labor union figures may have influenced his writing. He joined the League of American Writers, a Communist organization, in 1935. Steinbeck was mentored by radical writers Lincoln Steffens and his wife Ella Winter. Through Francis Whitaker, a member of the Communist Party USA's John Reed Club for writers, Steinbeck met with strike organizers from the Cannery and Agricultural Workers' Industrial Union. In 1939, he signed a letter with some other writers in support of the Soviet invasion of Finland and the Soviet-established puppet government.