On May 17, 1917, the Porto Rico Regiment of Infantry was sent to guard the Panama Canal in defense of the Panama Canal Zone One of the Puerto Ricans who distinguished himself during World War I was Lieutenant Frederick Lois Riefkohl of the US Navy, who on August 2, 1917, became the first known Puerto Rican to be awarded the Navy Cross. The Navy Cross, which is the second-highest medal after the Medal of Honor, that can be awarded by the U.S. Navy, was awarded to Lt. Riefkohl for his actions in an engagement with an enemy submarine. Lt. Riefkohl, who was also the first Puerto Rican to graduate from the United States Naval Academy, served as a rear admiral in World War II.