Not being in the military myself, I had just always assumed that the Bronze Star was awarded for battlefield heroism, but the actual description of it is different:
The Bronze Star Medal may be awarded by the Secretary of a military department or the Secretary of Homeland Security with regard to the Coast Guard when not operating as a service in the Navy, or by such military commanders, or other appropriate officers as the Secretary concerned may designate, to any person who, while serving in any capacity in or with the Army, Navy, Marine Corps, Air Force, or Coast Guard of the United States, after 6 December 1941, distinguishes, or has distinguished, himself by heroic or meritorious achievement or service, not involving participation in aerial flight—
(a) while engaged in an action against an enemy of the United States;
(b) while engaged in military operations involving conflict with an opposing foreign force; or
© while serving with friendly foreign forces engaged in an armed conflict against an opposing armed force in which the United States is not a belligerent party.
Apparantly the V device distinguishes what type of achievement the medal was awarded for:
The Valor device (or “V device”) is authorized by all services and identifies the award as resulting from an act of combat heroism (as in the case of the Army and Air Force) or signifying that the medal was earned in combat (as in the case of the Navy), thus distinguishing it from meritorious achievement awards