 Born in Dalhem, Thys graduated at the École de guerre, before entering into the service of king Leopold II of Belgium in 1876, as secretary of the colonial businesses.After the return of Henry Morton Stanley, the king sent Thys to England to propose a new expedition to Central Africa on behalf of the Association Internationale Africaine.Thys was actively involved in the organisation of the first expeditions which would lead to the constitution of the Congo Free State.