United States in World War I
On March 21, 1915, Lt. Teófilo Marxuach was the officer of the day at the El Morro fortress. The "Odenwald" (built in 1903 and not to be confused with the German World War II warship of the same name) was an armed German supply ship which tried to force its way out of the bay and deliver supplies to the German submarines waiting in the Atlantic Ocean. Lt. Marxuach gave the order to open fire on the ship, which was forced to return; its supplies were confiscated. The shots ordered by Lt. Marxuach are widely regarded to be the first shots fired by the United States in World War I, although the first actual wartime shot fired by the U.S. came on the day war was declared, during the scuttling of the SMS Cormoran off Guam.