The U.S. annexed the former Spanish colonies of Puerto Rico, the Philippines and Guam. The notion of the United States as an imperial power, with colonies, was hotly debated domestically with President McKinley and the Pro-Imperialists winning their way over vocal opposition led by Democrat William Jennings Bryan, who had supported the war. The American public largely supported the possession of colonies, but there were many outspoken critics such as Mark Twain, who wrote "The War Prayer" in protest. Roosevelt returned to the United States a war hero, and he was soon elected governor of New York and then became the vice president. At the age of 42, he became the youngest person to become president after the assassination of President McKinley.