In April 1914, during the Mexican Revolution, the Tampico Affair occurred, and escalated as a result of a twenty-one gun salute (or more specifically, the lack of one). Nine unarmed U.S. sailors were arrested in Tampico, Tamaulipas, Mexico, for entering an off-limit area at a fuel loading station. Despite being released, the U.S. Naval commander demanded an apology and a twenty-one gun salute. The apology was provided, but not the salute, giving President Woodrow Wilson reason to order the U.S. occupation of the port of Veracruz.