An international movement with national groups in thirty countries, Pugwash works to avoid nuclear war. It began with an appeal by Bertrand Russell, who was joined by ten other scientists, to members of the international scientific community to "assemble in conference to appraise the perils that have arisen as a result of the development of weapons of mass destruction." The first conference was held in July 1957 in Pugwash, Nova Scotia. Since then the conferences have been held at a variety of international locations on an annual and semi-annual basis. Members of the world scientific community gather in an unofficial capacity to discuss nuclear proliferation and propose measures by which the scientific community can influence governments in reaching international agreements limiting the accumulation and use of nuclear weapons. Since the late 1960s, topics have broadened to include environmental pollution, world overpopulation, the energy crisis, and problems of the developing nations.