What significant conflict did Theodore Roosevelt help mediate between Japan and Russia?

The significant conflict that Theodore Roosevelt helped mediate was the Russo-Japanese War. This conflict took place from 1904 to 1905 and involved Japan and Russia fighting over imperial ambitions in Manchuria and Korea. Roosevelt played a crucial role in brokering peace between the two nations through his facilitation of the Treaty of Portsmouth in 1905. His successful mediation efforts not only earned him international acclaim but also led to him receiving the Nobel Peace Prize in 1906, marking a significant moment in U.S. diplomacy and showcasing America's growing involvement in international affairs during the era of imperialism. Roosevelt's actions highlighted the United States' position as a mediator in global conflicts, particularly in Asia, which would have lasting implications for U.S.-Japan relations in the following decades.