United States involvement in the Mexican Revolution 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. 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 city 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
Import-Export Clause a harbor and were distinct from charges imposed for pilotage or loading and unloading cargo. In "Clyde Mallory Lines v. Alabama", the Supreme Court explained that the prohibition on tonnage duties "was due to the desire of the framers to supplement [the Import-Export Clause] ... by forbidding a corresponding tax on the privilege of access by vessels to the ports of a state, and to their doubts whether the Commerce Clause would accomplish that purpose." The Tonnage Clause was also, like the Import-Export Clause, intended to prevent states with convenient ports from taxing goods destined to states which lacked good