Following the independence of the United States of America in 1776 and the independence of Haiti in 1804, the struggle for independence after 1810 by the Hispanic American nations evoked a sense of unity, especially in South America, where—under Simón Bolívar in the north and José de San Martín in the south—there were cooperative efforts. Francisco Morazán briefly headed a Federal Republic of Central America. Early South American Pan-Americanists were also inspired by the American Revolutionary War, where a suppressed and colonized society struggled, united, and gained its independence. In the United States, Henry Clay and Thomas Jefferson set forth the principles of Pan-Americanism in the early 19th century, and soon afterward the United States declared through the Monroe Doctrine a new policy with regard to interference by European nations in the affairs of the Americas.