8 C.F.R. § 329.1
As used in this part:
Honorable service and separation means service and separation from service which the executive department under which the applicant served determines to be honorable, including:
(1) That such applicant had not been separated from service on account of alienage;
(2) That such applicant was not a conscientious objector who performed no military, air or naval duty; and
(3) That such applicant did not refuse to wear a military uniform.
Service in an active duty status in the Armed Forces of the United States means active service in the following organizations:
(1) United States Army, United States Navy, United States Marines, United States Air Force, United States Coast Guard; or
(2) A National Guard unit during such time as the unit is Federally recognized as a reserve component of the Armed Forces of the United States and that unit is called for active duty.
World War I means the period beginning on April 6, 1917, and ending on November 11, 1918.
8 C.F.R. §329.1