Mexican Revolution revolution was in 1914, during the "Ypiranga" incident. When United States intelligence agents received word that the "Ypiranga", a German merchant ship, contained illegal firepower for Huerta, President Wilson ordered American troops to the port of Veracruz to stop the ship from docking. Wilson never actually declared war on Mexico. The United States skirmished with Huerta's troops in Veracruz. The "Ypiranga" successfully docked at another port and unloaded the arms, which greatly angered Wilson. The ABC Powers arbitrated and U.S. troops left Mexican soil, but the incident added to already tense Mexican-American relations. In 1916, in retaliation for Pancho Villa's
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