At the suggestion of Czar Nicholas II of Russia, the First International Peace Conference was held in The Hague. 26 nations attended.
Although the conference failed to achieve its primary objective, the limitation on armaments, it did adopt conventions defining the state of belligerency and adopted the Convention for the Pacific Settlement of International Disputes thus creating the Permanent Court of Arbitration. [Encyclopaedia Britannica]
This was the second attempt by a sovereign to call for some sort of international peace conference. The first such effort was made by Napoleon III in the 1860s. [Modernity and Millennium by Juan Cole p131-135]