Pete Ellis was born on December 19, 1880, in Iuka, Kansas. He enlisted in the U.S. Marine Corps on September 3, 1900, and served at the Washington Navy Yard until receiving a commission as a 2nd Lt in the Marine Corps on December 21, 1901. His next assignment was to Marine Barracks, Charleston Navy Yard in Boston, Massachusetts, from January to March 1902, followed by service at Marine Barracks, Washington, D.C., from March to April 1902. Lt Ellis served as adjutant for the 1st Marine Regiment in the Philippines from April 1902 to January 1903, followed by service as Marine Detachment Commander aboard the battleship USS Kentucky (BB-6) from January 1903 to May 1904. His next assignment was to the Marine Barracks in Washington, D.C., from June to September 1904, and then as Quartermaster at Mare Island, California, from September 1904 to December 1905. Lt Ellis served as a recruiting officer in Oakland, California, and Des Moines, Iowa, from December 1905 to April 1907, and then returned to Mare Island until deploying to the Philippines in November 1907. He served as the adjutant of the 2nd Marine Regiment in the Philippines from November 1907 to February 1908, executive officer of Company E, 2nd Marine Regiment, from February to June 1908, and then as commander of Company F, 2nd Marine Regiment, from July to May 1909. Capt Ellis again served as adjutant for the 2nd Marine Regiment from May 1909 to January 1911, followed by service at the Washington Navy Yard from March to May 1911. He next attended the Naval War College in Newport, Rhode Island, remaining on the staff of the college until October 1913. His next assignment was as Intelligence Officer with the Advanced Base Force at the Philadelphia Navy Yard from October 1913 to March 1914, followed by service as Intelligence Officer, secretary, and aide-de-camp to the governor-designate on Guam from March 1914 to August 1915. He then served as aide-de-camp to the Commandant of the Marine Corps from August 1915 to May 1917, followed by service assisting in the establishment of Marine Corps Base Quantico, Virginia, from May to October 1917. Maj Ellis next deployed to France as a liaison and observer from October 1917 to January 1918, and then deployed again, this time with the 6th Marines in France, from May 1918 until the end of the war. He remained in France as part of the 4th Marine Brigade until returning to the U.S. in August 1919, and then served at Quantico until April 1920. Col Ellis next served as an intelligence officer in the Dominican Republic from April to December 1920, followed by service as head of the intelligence section of the Division of Operations and Training with Headquarters Marine Corps from December 1920 to May 1921. His next assignment was as the first spy in the U.S. Marine Corps, when he took on clandestine reconnaissance missions in the Pacific to monitor Japanese military buildup there. Col Ellis died under mysterious circumstances on the Japanese-held island of Palau in the Caroline Islands on May 12, 1923.

His Navy Cross Citation reads:

he President of the United States of America takes pleasure in presenting the Navy Cross to Lieutenant Colonel Earl Hancock Ellis, United States Marine Corps, for exceptionally meritorious and distinguished service as Adjutant, 4th Brigade Marines, 2d Division, A.E.F. Lieutenant Colonel Ellis displayed utter disregard of personal hardship and danger, energetic application and an unfailing devotion to the duties of his office. He has ever shown himself ready for any emergency, even when he had been without sleep or rest for several days and nights at a time. His keen analytical mind, quick grasp of intricate problems, resourcefulness, decision and readiness to take prompt action on important questions arising during the temporary absence of the Brigade Commander within the Brigade, have contributed largely to the success of the Brigade, rendered his services invaluable and won for him the high esteem and complete confidence of the Brigade Commander.