A nuclear triad refers to a nuclear arsenal which consists of three components. The purpose of having a trifurcated nuclear capability is to significantly reduce the possibility that an enemy could destroy all of a country's nuclear forces in a first strike attack; this, in turn, ensures a credible threat of a second strike, and thus increases a nation's nuclear deterrence.
Traditional Components
While traditional nuclear strategy holds that a nuclear triad provides the best level of deterrence from attack, in reality, most nuclear powers do not have the military budget to sustain a full triad. Only the United States and Russia have maintained nuclear triads for most of the nuclear age. And both the US and the former Soviet Union composed their triads along the same lines, including the following components:
strategic bombers (carrier-based or land-based; armed with bombs or missiles)
To be considered a part of a nuclear triad, weapons must have a first- or second-strike function; without this, they are regarded as tactical nuclear weapon.
The triad also gives the commander the possibility to use different types of weapons for the appropriate strike:
ICBMs allow for a long-range strike launched from a controlled or friendly environment. If launched from a fixed position, such as a missile silo, they are vulnerable to a first strike, though their interception once aloft is substantially difficult.
SLBMs, launched from submarines, allow for a greater chance of survival from a first strike, giving the commander a second-strike capability. Their limited range, however, means that submarines must often be closer to its target than desirable, allowing for potential detection and tracking by an enemy attack submarine or a SOSUS-like system.
Strategic bombers have greater flexibility in their deployment and weaponry. They can serve as both a first- and second-strike weapon. A stealth B-2 Spirit bomber armed with stealth AGM-129 ACM missiles, for example, could be classified as a first-strike weapon. A number of conventional bombers kept at fail-safe points would constitute a second-strike weapon.
Non-triad nuclear powers
As indicated above, not all nuclear powers have triads.
France—The Force de frappe possessed, in the past, a "traditional" nuclear triad, though it currently possesses only sea-based and air-based components.
Israel—In addition to its Jericho MRBMs and aircraft, Israel is unique in reportedly using submarine-launched cruise missiles as part of its deterrent (as opposed to ballistic missiles).
India—India developed Sagarika (under the title Project K-15) a nuclear-capable submarine-launched ballistic missile,which is being integrated with the Advanced Technology Vessel that is expected to begin sea trials by 2009.Shaurya missile, a land based version of the sagarika which can be launched from underground silos provides India with a significant second strike capability. Along with currently operational [[Agni (missile)|Agni III],17 long range strategic nuclear bombers and 116, 4.5 generation fighter jets capable to use nuclear weapons,India will soon be a full triad nuclear power.
Pakistan— The country lack a dedicated naval component to its nuclear deterrent. Existing or planned cruise missiles, however, are thought to be adaptable for this purpose.
Other nuclear delivery systems
There is nothing in nuclear strategy to mandate only these three delivery systems. For example, orbital weapons or spacecraft for purposes of orbital bombardment using nuclear devices could be developed, and would not fit into the categories listed above. However, space-based weapon systems used for weapons of mass destruction have been banned under the Outer Space Treaty and the SALT II treaty.
