Stalin's repressive regime as leader of the former Soviet Union prevented Moscow from hosting the prestigious Seventh International Genetical Congress in 1937. After a two year delay, Edinburgh was selected as the host, with F.A.E. Crew as organising secretary. The Congress went ahead despite 50 Russian scientists withdrawing at the last minute, as well as the outbreak of war across Europe during the Congress itself. Many delegates departed early in attempts to reach their home country; some remained permanently in Edinburgh.