an established fact, with the democratically elected president Madero murdered and his family in exile. President Wilson did not recognize the Huerta as the legitimate head of the Mexican government, and from March to October 1913, Wilson pressured Huerta to resign. Wilson urged the European powers to refrain from recognizing Huerta's government. Huerta announced elections with himself as a candidate. In August 1913, Wilson imposed an arms embargo on Huerta's regime, reversing his previous easy access to arms. In late August Huerta withdrew his name from consideration as a presidential candidate, and his foreign minister Federico Gamboa stood for election. The U.S. was enthusiastic about Gamboa's candidacy and supported the new regime, but not Huerta himself. The U.S. pressured revolutionary opponents, including the newly emerged anti-Huerta leader Venustiano Carranza, to sign on to support a potential new Gamboa government. Carranza refused. A series of rebellions broke out in Mexico against Huerta's regime, especially in the North (Sonora, Chihuahua, and Coahuila), where the U.S. allowed arms sales to the revolutionaries. Fighting continued in Morelos under Emiliano Zapata, but the conflict there was a regional one with no U.S. involvement. Unlike the brief rebellions that helped bring Madero to power in 1910–1911, Mexico descended into civil war, with the U.S. backing revolutionary factions in the north. The involvement of the U.S. in larger conflicts with its diplomatic and economic rivals in Mexico, particularly Great Britain and Germany, meant that foreign powers affected the way the Mexican situation played out, even if they did not intervene militarily. When U.S. agents discovered that the German merchant ship, the Ypiranga, was carrying arms to Huerta's regime, President Wilson ordered troops to the port of Veracruz to stop the ship from docking. The U.S. did not declare war on Mexico but the U.S. troops carried out a skirmish against Huerta's forces in Veracruz. The Ypiranga managed to dock at another port, which infuriated Wilson. On April 9, 1914, Mexican officials in the port of Tampico, Tamaulipas, arrested a group of U.S. sailors — including at least one taken from on board his ship, and thus from U.S. territory. After Mexico refused to apologize in the terms that the U.S. had demanded, the U.S. Navy bombarded the port of Veracruz and occupied Veracruz for seven months. Woodrow Wilson's actual motivation was his desire to overthrow Huerta, whom he refused to recognize as Mexico's leader; the Tampico Affair