 The doctor served on transports in the Atlantic during World War I, earning the Navy Cross for attending the sick and wounded when troop transport "President Lincoln" was torpedoed 31 May 1918.He entered the Regular Navy in 1919, and served in various ships and at Naval Hospitals in the United States and abroad in the years that followed.Blackwood served the people of Haiti 1927 to 1930 when assigned to a Public Health unit on that island.