The American Defense Service Medal (ADSM) was established per Executive Order 8808, dated June 28, 1941, by President Franklin D. Roosevelt and announced in War Department Bulletin 17. The criteria was announced in Department of the Army Circular 44 in Feb. 13, 1942.
The American Defense Service Medal will be awarded to all persons who served on active duty at any time between Sept. 8, 1939 and Dec. 7, 1941, if the active duty order specified service for a 12-month period or longer. A Foreign Service Clasp is attached to the ribbon and medal if the same requirements are met and the service was performed outside the continental United States (CONUS).
The medal is 1.25 inches in diameter, bearing in front an armed figure symbolic of defense under the inscription American Defense. The ribbon is basically yellow, with blue, white, and red stripes right to left and left to right symmetrically near the edges.
Service Star - Worn in lieu of clasps when wearing the American Defense Service Medal as a ribbon on a military uniform
Concerning Naval Service Awards:
(1) The American Defense Service Medal will be awarded to all persons in the naval service who served on active duty at any time between 8 September 1939 and 7 December 1941, both dates inclusive.
(2) Naval Reserve personnel on training duty under orders must have served at least 10 days in such duty. Person ordered to active duty for physical examination and subsequently disqualified are not entitled to this award. Reserve officers ordered to ships of the fleet for training duty (cruise) and officers serving on board ships for temporary additional duty from shore stations are not considered "regularly attached" and are not entitled to the fleet clasp.
(3) A service clasp, "Fleet" or "Base," is authorized to be worn on the ribbon of the medal by each person who performed duties as set forth below. No person is entitled to more than one such clasp.
(a) Fleet or sea. -- For service on the high seas while regularly attached to any vessel or aircraft squadron of the Atlantic, Pacific or Asiatic Fleet; to include vessels of the Naval Transportation Service and vessels operating directly under the Chief of Naval Operations. [Note: The "Sea" clasp was issued to Coast Guard personnel under similar qualifications as the Navy's "Fleet" clasp.]
(b) Base. -- For service on shore at bases and naval stations outside the continental limits of the United States. (Duty in Alaska is considered outside the continental limits of the United States.)
(4) A bronze star, three-sixteenths of an inch in diameter, will be worn on the service ribbon in lieu of any clasp authorized.
(5) Navy, Marine Corps, and Coast Guard personnel, who served on the following vessels operating in actual or potential belligerent contact with the Axis forces in the Atlantic Ocean between the dates set below the ship in the table below are authorized to wear upon the American Defense Service Medal service ribbon, a bronze letter "A" in lieu of the bronze star. Such letter shall be one-fourth inch in height and shall be worn centered on the ribbon. When the "A" is worn, no star shall be worn upon the ribbon (Executive Order No. 8808 of 28 June 1941; Navy Department General Order No. 172 of 20 April 1942).
Source: 1948, 1953 U.S. Navy Awards Manual