United States in World War I
Lieutenant Teófilo Marxuach (retired as a Lieutenant Colonel), a native of Arroyo, Puerto Rico, fired the first shot in what is considered to be the first shot of World War I fired by the regular armed forces of the United States against any ship flying the colors of the Central Powers. Marxuach, who was a member of the "Porto Rico Regiment of Infantry" and Officer of the Day, on March 25, 1915, opened fire on the "Odenwald", an armed German supply vessel, when it was trying to force its way out of San Juan's bay. The shots ordered by Lt. Marxuach were the first fired by the United States in World War I.