The islands had been ceded by Spain to the United States alongside Puerto Rico and Guam as a result of the latter's victory in the Spanish–American War. As it became increasingly clear the United States would not recognize the First Philippine Republic, the Philippine–American War broke out. The war resulted in the deaths of 250,000 to 1 million civilians, mostly due to famine and disease. After the defeat of the First Philippine Republic, an American civilian government was established. American forces continued to secure and extend their control over the islands, suppressing an attempted extension of the Philippine Republic, securing the Sultanate of Sulu, and establishing control over interior mountainous areas that had resisted Spanish conquest.