The Tampico Affair began as a minor incident involving United States Navy sailors and the Mexican Federal Army loyal to Mexican dictator General Victoriano Huerta. On April 9, 1914, nine sailors had come ashore to secure supplies and were detained by Mexican forces. Commanding Admiral Henry Mayo demanded that the US sailors be released, and that Mexico issue an apology, raise and salute the US flag, and perform a 21-gun salute. Mexico refused the demand. US President Woodrow Wilson backed the demand, and the conflict escalated when the Americans occupied the port city of Veracruz for more than six months. This contributed to the fall of Huerta, who resigned in July 1914. Since the US had not had diplomatic relations with Mexico since Huerta's seizure of power in 1913, the ABC powers Argentina, Brazil, and Chile offered to mediate the conflict, in the Niagara Falls peace conference, held in Canada. The American occupation of Veracruz caused widespread anti-American sentiment.