National Defense Service Medal (with Service Star)

Insituted by President Dwight D. Eisenhower, the National Defense Service Medal was issued to members of the US Military who served during designated time periods in a national emergency. The original times periods were 1950-1954 (Korean War), 1951-1974 (Viet Nam War), and 1990 to 1995 (Gulf War). For service in the Gulf War and “War on Terrorism,” it is also authorized for active members of the military reserve in good standing.

Additional awards in the same category are denoted by Service Stars, also known as “battle stars,” “campaign stars,” or “engagement stars.”

General Clark earned the medal with one additional star.

Source:
http://en.wikipedia.org/wiki/National_Defense_Service_Medal