Roosevelt was lieutenant colonel of the Rough Rider Regiment during the Spanish-American War. He led a charge at the battle of San Juan. A few years later Roosevelt became a Republican candidate for Governor in New York in 1898, which he won. He became president in 1904. President Roosevelt became a mediator between Russia and Japan in June 1905. He asked their belligerents to appoint plenipotentiaries to bargain on the conditions of peace. They met two months later in Portsmouth, New Hamsphire, and came to a conclusion of a peace treaty in September 1905. He won the Nobel Peace Prize for mediating the Russo-Japanese War, reached a Gentleman's Agreement on immigration with Japan, and sent the Great White Fleet on a goodwill tour of the world. Roosevelt steered the United States more actively into world politics. He liked to quote a favorite proverb, "Speak softly and carry a big stick. . . . "

Roosevelt crusaded endlessly through all types of matters, attracting exciting audiences with his high-pitched voice, jutting jaw, and pounding fist. "The life of strenuous endeavor" was a must for those around him, as he went around with his five younger children and led ambassadors on hikes through Rock Creek Park in Washington, D.C.

Roosevelt left Presidency in 1909, then ran again in 1912, reporters he once remarked that he felt as fit as a bull moose, the name of his new party.