The Russo-Japanese War (8 February 1904 – 5 September 1905) was "the first great war of the 20th century." It grew out of rival imperial ambitions of the Russian Empire and Japanese Empire over Manchuria and Korea. The major theatres of operations were Southern Manchuria, specifically the area around the Liaodong Peninsula and Mukden; and the seas around Korea, Japan, and the Yellow Sea.

Russians sought a warm water port on the Pacific Ocean, for their navy as well as for maritime trade. Vladivostok was only operational during the summer season, but Port Arthur would be operational all year. From the end of the First Sino-Japanese War and 1903, negotiations between Russia and Japan had proved impractical. Japan chose war to gain dominance in Korea. After discussions broke down in 1904, the Japanese Navy attacked the Russian eastern fleet at Port Arthur, a naval base in the Liaotung province leased to Russia by China, which led to war. The Russians were poorly organized and the Japanese defeated them in a series of battles on land and at sea.

Theodore "Teddy" Roosevelt ( /ˈroʊzəvɛlt/ ROH-zə-velt; October 27, 1858 – January 6, 1919) was the 26th President of the United States of America (1901–1909). He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his "cowboy" persona and robust masculinity. He was a leader of the Republican Party and founder of the short-lived Progressive ("Bull Moose") Party of 1912. Before becoming President, he held offices at the city, state, and federal levels. Roosevelt's achievements as a naturalist, explorer, hunter, author, and soldier are as much a part of his fame as any office he held as a politician. Roosevelt was 42 years old when sworn in as President of the United States in 1901, making him the youngest president ever; he beat out the youngest elected president, John F. Kennedy, by only one year. Roosevelt was also one of only three sitting presidents to have won the Nobel Peace Prize, the other two being Woodrow Wilson and Barack Obama.