The large number of CVBGs used by the United States reflects in part a division of labor during the Cold War, in which the United States assumed primary responsibility for blue water operations and for safeguarding supply lines between the United States and Europe, while the NATO allies assumed responsibility for brown and green water operations.
The need for a battle group is due to the fact that while the aircraft carrier has the ability to project a large amount of air power, it is vulnerable to attack from other surface ships and submarines. One way of looking at the CVBG is that the carrier performs the mission assigned to it while the primary role of the other ships is to protect the carrier.
CVBGs have no definitive specification and are formed and dissolved on an as-needed basis, and one may be different from another. However, they all are comprised of similar types of ships, and a typical carrier battle group might have:
During the Cold War, the main role of the CVBG in case of conflict with the Soviet Union would have been to protect Atlantic supply routes between the United States and Europe. Because the Soviet Union lacked its own carriers, a situation of duelling aircraft carriers would have been unlikely. The main scenario of interest would have been an attack against a CVBG using large number of anti-ship cruise missiles. The attempted use of anti-ship missiles against a carrier group was part of Argentina's efforts against Britain in the Falklands War.
In the late 20th and early 21st centuries, most of the uses of CVBGs by United States have been in situations in which their use has been uncontested. The main scenario involving carriers which has occupied the interest of naval strategists has been a conflict between the United States and the People's Republic of China over Taiwan. There is a consensus among observers that most of the military effort expended by the People's Liberation Army since the 1990s has been to at least complicate the deployment of a CVBG in a Taiwan straits conflict.
There is debate in naval warfare circles as to the viability of carrier battle groups in 21st century naval warfare. Proponents of the CVBG argue that it provides unmatched fire power and force projection capabilities. Opponents argue that CVBGs are increasingly vulnerable to cruise missiles and arsenal ships, were designed for Cold War scenarios, and are less useful in establishing control of areas close to shore.