After the outbreak of World War II, the French government sent Rapkine to London in January 1940, on an official mission to secure a supply of coal for French industrial and military purposes. While in England, he assisted James Crowther in creating an Anglo-French Society of Sciences to formalize scientific cooperation between the two countries. In June 1940, after France's surrender to Germany, Rapkine advocated for the Society to help French scientists find refuge in the United Kingdom, but the Society dissolved when hostilities between France and England foreclosed scientific cooperation. Rapkine and Henri Laugier left London to continue their efforts in the United States.