The Russo-Japanese War (1904-1905) was fought between the Empire of Japan and the Russian Empire over rival imperial ambitions in Manchuria and Korea.
The Russian and Japanese empires were exhausted by the war, faced domestic unrest, and having little to gain by continuing the struggle, accepted President Theodore Roosevelt’s offer to mediate.
Roosevelt served as mediator at the peace conference, which was held at the Portsmouth Naval Shipyard in Kittery, Maine, U.S. (August 9–September 5, 1905). In the resulting Treaty-of-Portsmouth, Japan gained control of the Liaodong Peninsula (and Port Arthur) and the South Manchurian Railway (which led to Port Arthur) as well as half of Sakhalin Island. Russia agreed to evacuate southern Manchuria, which was restored to China, and Japan’s control of Korea was recognized. Roosevelt was awarded the Nobel Peace Prize for his role in ending the conflict. — Encyclopedia Britanica
The signing of the treaty settled immediate difficulties in the Far East and created three decades of peace between the two nations. — Wikipedia
The current war between Russia and Ukraine could end in this way. Already both sides have little to gain by continuing the struggle. What might be lacking is an impartial mediator. Perhaps Turkish President Erdogan can fill this role.