Barclay promoted arbitration, conciliation and international law. He was president of the British Chamber of Commerce 1899-1900. Barclay was a member of the Institute of International Law and deputy Chairman of the International Law Association.
Martens advocated international arbitration and he also worked to establish a codification of the laws of war. He often acted as mediator in disputes between European states.Author of the book "La paix et la guerre".
Roosevelt mediated in the Russo-Japanese War (1904-05). His efforts led to the peace treaty of 1905.