He previously served as the 25th vice president  under President William McKinley from March to September 1901 and as the 33rd governor of New York from 1899 to 1900. Assuming the presidency after McKinley's assassination, Roosevelt emerged as a leader of the Republican Party and became a driving force for anti-trust and Progressive policies.
A sickly child with debilitating asthma, he overcame his health problems as he grew by embracing a strenuous lifestyle. Roosevelt integrated his exuberant personality and a vast range of interests and achievements into a "cowboy" persona defined by robust masculinity. He was home-schooled and began a lifelong naturalist avocation before attending Harvard College. His book The Naval War of 1812 (1882) established his reputation as a learned historian and popular writer. Upon entering politics, Roosevelt became the leader of the reform faction of Republicans in New York's state legislature. His first wife and mother died on the same night, devastating him psychologically. He recuperated by buying and operating a cattle ranch in the Dakotas. Roosevelt served as Assistant Secretary of the Navy under President McKinley, and in 1898 helped plan the highly successful naval war against Spain. 