The most intensive period of Soviet military collaboration with Weimar Germany was 1930–1932. On June 24, 1931, an extension of the 1926 Berlin Treaty was signed, though it was not until 1933 that it was ratified by the Reichstag due to internal political struggles. Some Soviet mistrust arose during the Lausanne Conference of 1932, when it was rumored that German Chancellor Franz von Papen had offered French Prime Minister Édouard Herriot a military alliance.