A nuclear triad refers to a nuclear arsenal which consists of three components, traditionally strategic bombers, intercontinental ballistic missiles (ICBMs), and submarine-launched ballistic missiles (SLBMs). The purpose of having a three-branched nuclear capability is to significantly reduce the possibility that an enemy could destroy all of a nation'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. Both the US and the Soviet Union composed their triads along the same lines, including the following components:
- Bomber aircraft capable of delivering nuclear bombs (carrier-based or land-based; usually armed with long-range missiles).
- Land-based missiles (MRBMs or ICBMs).
- Ballistic missile submarines (SSBNs). Nuclear missiles launched from ships or submarines. Although in early years the US Navy sea leg was carrier aircraft based with a very short period using sub launched cruise missiles such as the Regulus before SLBMs were ready to be deployed.
The triad also gives the commander in chief 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, Some ICBMs are either rail or road mobile. Medium-range ballistic missiles and long-range ground-launched cruise missiles were also assigned for strategic targets but forbidden by treaty to the US and Russia.
- SLBMs, launched from submarines, allow for a greater chance of survival from a first strike, giving the commander a second-strike capability. Some long-range submarine-launched cruise missiles are counted towards triad status; this was the first type of submarine-launched strategic second-strike nuclear weapon before ballistic missile submarines became available.
- Strategic bombers have greater flexibility in their deployment and weaponry. They can serve as both a first- and second-strike weapon. A bomber armed with AGM-129 ACM missiles, for example, could be classified as a first-strike weapon. A number of bombers often with aerial refueling aircraft kept at safe points would constitute a second-strike weapon. Some lighter aircraft can be used as either a first-strike weapon or if dispersed at small airfields or aboard an aircraft carrier can reasonably avoid a counterstrike giving them regional second-strike capacity, aircraft such as the Mirage 2000, F-15E, A-5 Vigilante, Sea Harrier, or FB-111 are or were tasked part or full-time with land or sea-based strategic nuclear attack missions. An aerial refueling fleet supports intercontinental strategic operations both for heavy bombers and smaller aircraft; it also makes possible around the clock airborne standby of bombers and command aircraft making these airborne assets nearly impossible to eliminate in a first strike.
Tactical nuclear weapons are used in air, land and sea warfare. Air-to-air missiles and rockets, surface-to-air missiles, and small air-to-ground rockets, bombs, and precision munitions have been developed and deployed with nuclear warheads. Ground forces have included tactical nuclear artillery shells, surface-to-surface rockets, land mines, medium and small man-packable nuclear engineering demolition charges, even man-carried or vehicle-mounted recoilless rifles. Naval forces have carried nuclear-armed naval rocket-assisted and standard depth charges and torpedoes, and naval gunnery shells. Tactical nuclear weapons and the doctrine for their use is primarily for use in a non-strategic warfighting role destroying military forces in the battle area; they are not counted toward triad status.
Triad nuclear powers 
The following nations are considered triad nuclear powers. They possess nuclear forces consisting of land-based missiles, ballistic or long-range cruise missile submarines, and strategic bombers or long-range tactical aircraft.
United States 
The United States operates Minuteman ICBMs from underground hardened silos, Trident SLBMs carried by Ohio-class submarines, it also operates B-52, B-2 strategic bombers, as well as land-based tactical aircraft, some capable of carrying strategic and tactical B61 and large strategic B83 gravity bombs, and AGM-86 ALCMs. While the US no longer keeps nuclear armed bombers on airborne alert, it has the ability to do so, along with the airborne nuclear command and control aircraft with its fleet of KC-10 and KC-135 aerial refueling planes. Previous to development of submarine-launched ballistic missiles, the US Navy strategic nuclear role was provided by aircraft carrier–based bombers and, for a short time, submarine-launched cruise missiles. With the end of the cold war, the US never deployed the rail-mobile version of the Peacekeeper ICBM or the road mobile Midgetman small ICBM. The US destroyed its stock of road-mobile Pershing II IRBMs and ground-launched cruise missiles in accordance with the INF treaty. The US also has shared strategic nuclear weapons and still deploys shared tactical nuclear weapons to some NATO countries.
Also a nuclear power, Russia inherited the arsenal of all of the former Soviet states; this consists of silo-based as well as rail and road mobile ICBMs, sea-based SLBMs, strategic bombers, strategic aerial refueling aircraft, and long-range tactical aircraft capable of carrying gravity bombs, standoff missiles, and cruise missiles. The Russian Strategic Rocket Forces have ICBMs able to deliver nuclear warheads, silo-based R-36M2 (SS-18), silo-based UR-100N (SS-19), mobile RT-2PM "Topol" (SS-25), silo-based RT-2UTTH "Topol M" (SS-27), mobile RT-2UTTH "Topol M" (SS-27), mobile RS-24 "Yars" (SS-29) (Future replacement for R-36 & UR-100N missiles). Russian strategic nuclear submarine forces are equipped with the following SLBM's, R-29R "Vysota", NATO name SS-N-18 "Stingray", RSM-54 R-29RMU "Sineva", NATO name SS-N-23 "Skiff" and the R-29RMU2.1 "Liner" are in use with the Delta class submarine, but the RSM-56 R-30 "Bulava", NATO name SS-NX-32 is under development for the Borei class submarine. The Russian Air Force operates supersonic Tupolev Tu-22M, and Tupolev Tu-160 bombers and the long range turboprop powered Tupolev Tu-95, they are all mostly armed with strategic stand off missiles or cruise missiles such as the KH-15 and the KH-55. These bombers and nuclear capable strike aircraft such as the Sukhoi Su-24 are supported by Ilyushin Il-78 aerial refuelling aircraft. The USSR was required to destroy its stock of IRBMs in accordance with the INF treaty.
Emerging Triad Powers 
Unlike the US and Russia where strategic nuclear forces are enumerated by treaty limits and subject to verification, China, a nuclear power since 1964, is not subject to these requirements but may have a triad structure of some sort. China's nuclear force is much smaller than the US or Russia and is closer in number and capability to that of France or the UK. This force is mainly land-based missiles including ICBMs, IRBMs, and tactical ballistic missiles as well as cruise missiles. Unlike the US and Russia, China stores many of its missiles in huge underground tunnel complexes; US Representative Michael Turner referring to 2009 Chinese media reports said “This network of tunnels could be in excess of 5,000 kilometers (3,110 miles), and is used to transport nuclear weapons and forces,” the Chinese Army newsletter calls this tunnel system an Underground Great Wall of China. China has one Type 092 submarine that is reportedly inactive due to technical problems, and is working on several new Type 094 submarines carrying SLBMs although the reliability of the new type is also in question in addition the single type 094 boat has not received its SLBMs. There is an aging bomber force consisting of Xian H-6s with an unclear nuclear delivery role as well as several tactical aircraft types that could be equipped with nuclear weapons. The PLAAF has a limited capability fleet of H-6 bombers modified for aerial refuelling as well as forthcoming Russian Ilyushin Il-78 aerial refuelling tankers.
India maintains a no first use nuclear policy and has been developing a nuclear triad capability as a part of its credible minimum deterrence doctrine. India's nuclear-weapons program possesses surface-to-surface missiles such as the Agni II and Agni III. In addition, the 5,000 km range Agni-V ICBM was also tested on 19 April 2012 which is believed to have a range of 5,800 km  and is expected to enter service by 2014. India's nuclear-weapons program possesses surface-to-air missiles like the Akash. India has nuclear-capable fighter aircraft such as the Dassault Mirage 2000H, Sukhoi Su-30 MKI, MIG-29 and HAL Tejas. Land and air strike capabilities are already in place under the control of Strategic Forces Command which is a part of Nuclear Command Authority (India). India operates a nuclear-powered submarine INS Chakra. INS Arihant is designed for strategic deterrence and will carry nuclear-tipped SLBMs. DRDO, is working on Sagarika, a submarine-launched ballistic missile. The missile was successfully tested for the fourteenth time on January 27, 2013 in the Bay of Bengal. The missile is expected to provide India with a credible sea-based second-strike capability. Also, K-4, with a range of about 5000 km and a part of the K Missile family is being developed.
Non-triad nuclear powers 
A former triad power, the French Force de frappe possesses sea-based and air-based nuclear forces through the Triomphant class ballistic missile submarines deployed with M45 intercontinental SLBMs armed with multiple warheads, nuclear capable Dassault Mirage 2000N fighter aircraft which replaced the long-range Dassault Mirage IV supersonic nuclear bomber and KC-135 aerial refuelling tankers in its inventory. France had S2 and S3 silo based IRBMs, the S3 with a 3,500 km range, but these have been phased out of service since the dissolution of the USSR. France operates aircraft with a nuclear strike role from its aircraft carrier.
United Kingdom 
The UK possesses sea-based nuclear forces through its Royal Navy Vanguard class ballistic missile submarines, deployed with Trident II intercontinental SLBMs armed with multiple warheads. The Royal Air Force operated V bomber strategic bombers throughout the Cold War. The planned UK silo-based IRBM, the Blue Streak missile, was cancelled as it was not seen as a credible deterrent, considering the population density of areas in the UK geologically suited for missile silos. The tactical Corporal surface-to-surface missile was operated by the British Army. The intermediate range Thor missile aimed at Soviet targets was operated briefly by the RAF but before the arrival of the Polaris SLBM. Previously having a nuclear strike mission for carrier-based Buccaneer attack aircraft and later Sea Harriers, the UK no longer deploys nuclear weapons for delivery by carrier-based naval aircraft or any other means other than the Vanguard submarine-launched Trident SLBM.
The Minimum Credible Deterrence (MCD), is a defense and strategic principle on which the atomic weapons program of Pakistan is based upon. This doctrine is not a part of the nuclear doctrine, which is designed for the use of the atomic weapons in a full scale declared war if the conditions of the doctrine are surpassed. Instead, the policy of the Minimum Credible Deterrence falls under minimal deterrence as an inverse to the Mutually Assured Destruction (MAD). In August 2012, The Economist magazine wrote an article stating that Pakistan was an emerging nuclear triad state. Pakistani plans of responding to any capture or pre-emptive destruction of their nuclear defences seems to be one reason why they are determined to develop a third leg, after air and land-based delivery systems, to Pakistan’s nuclear triad, consisting of nuclear-armed ships and submarines. As Iskander Rehman of the Carnegie Endowment, a think-tank, observes in a recent paper, Pakistani nuclear expansion and methods of delivery is drifting 'from the dusty plains of the Punjab into the world’s most congested shipping lanes.' "It is only a matter of time before Pakistan formally brings nuclear weapons into its own fleet.”
Pakistan possesses several ballistic missiles such as the Shaheen-1A and the Shaheen-II, both missiles having ranges of 1500 km and 2500 km respectively. They also contain systems said to be capable of carrying several nuclear warheads as well as being designed to evade missile-defense systems. Pakistan also possesses the Babur cruise missiles with a range up to 700 km. These land-based missiles are controlled by Army Strategic Forces Command of Pakistan Army.
The PAF has two dedicated units (No. 16 Black Panthers and No. 26 Black Spiders) operating 18 aircraft in each squadron of the JF-17 Thunder, believed to be the preferred vehicle for delivery of nuclear weapons. These units are major part of the Air Force Strategic Command, a command responsible for nuclear response. The PAF also operates a fleet of F-16 fighters, of which 18 were delivered in 2012 and confirmed by General Ashfaq Parvez Kayani, are capable of carrying nuclear weapons. The PAF also possesses the Ra'ad air-launched cruise missile which has a range of 350 km and can carry a nuclear warhead with a yield of between 10kt to 35kt.
In 2004, the Pakistan Navy established the Naval Strategic Forces Command and made it responsible for countering and battling naval-based weapons of mass destruction. It is believed by most experts that Pakistan is developing a sea-based variant of the Hatf VII Babur, which is a nuclear-capable ground-launched cruise missile.
North Korea 
North Korea has claimed to have indigenous nuclear weapons technology since a large underground explosion was detected in 2006. The DPRK has both aircraft and missiles which may be tasked to deliver nuclear weapons. The North Korean missile program is largely based on domestically produced variants of the Soviet Scud missile, some of which are sufficiently powerful to attempt satellite launch. The DPRK also has short-range ballistic missiles and cruise missiles. Western researchers believe the current generation of the DPRK's suspected nuclear weapons are too large to be fitted to the country's existing missile stock.
South Africa 
From the 1970s through the end of white minority rule, South Africa developed and deployed a small number of atomic weapons (perhaps up to six devices). These were intended to be delivered by the RSA's Canberra bomber force. South Africa also developed advanced ballistic missiles and a satellite launch vehicle which could have carried nuclear warheads. Before majority rule was introduced the RSA gave up its nuclear weapons.
Suspected triad nuclear powers 
Israel has been reported in congressional testimony by the US Department of Defense of having aircraft-delivered nuclear weapons as early as the mid-1960s, a demonstrated missile-based force since the mid-1960s, an IRBM in the mid-1980s, an ICBM in the early 2000s and the suspected second-strike capability arrived with the Dolphin class submarine and Popeye Turbo submarine-launched cruise missile. Israel is suspected of using their inventory of nuclear-capable fighter aircraft such as the long-range F-15E Strike Eagle, F-16 and formerly the F-4 Phantom, Dassault Mirage III, A-4 Skyhawk and Nesher. Israel has appreciable numbers of long-range tanker aircraft and aerial refueling capacity on its long-range fighter-bomber aircraft, this capacity was used in the 1985 long-range conventional strike against the PLO in Tunisia. Jane's Defence Weekly reports that the Israeli Dolphin class submarines are widely believed to be nuclear armed, offering Israel a second-strike capability with a demonstrated range of at least 1500 km in a 2002 test. According to an official report which was submitted to the American congress in 2004, it may be that with a payload of 1,000 kg the Jericho 3 gives Israel nuclear strike capabilities within the entire Middle East, Africa, Europe, Asia and almost all parts of North America, as well as within large parts of South America and North Oceania, Israel also has the regional reach of its Jericho 2 IRBM force. The existence of a nuclear force is often hinted at blatantly and evidence of an advanced weapons program including miniaturized and thermonuclear devices has been presented, especially the extensive photographic evidence given by former Israeli nuclear weapons assembler Mordechai Vanunu. There have been incidents where Israel has been suspected of testing, but so far Israel for diplomatic reasons and international pressure has not openly admitted to having operational nuclear weapons, and so is only a suspect triad state.
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 have been developed and silo deployed by the USSR from 1969 to 1983, these would not fit into the categories listed above. However, actual space-based weapon systems used for weapons of mass destruction have been banned under the Outer Space Treaty and launch ready deployment for the US and former USSR by the SALT II treaty. Another example is the US, UK, and France do or have previously included a strategic nuclear strike mission for carrier-based aircraft, which especially in the past were far harder to track and target with ICBMs or strategic nuclear bombers than fixed bomber or missile bases, permitting some second-strike flexibility; this was the first sea-based deterrent before the SLBM. The US and UK jointly explored an air-launched strategic ballistic nuclear missile, the Skybolt, but canceled the program in favor of submarine-based missiles. In 1974 a Lockheed C-5 Galaxy successfully tested an air launch of a Minuteman ICBM; this system was not deployed, but was used as a bargaining point in the SALT treaty negotiations with the USSR.
See also 
- Mutual Assured Destruction
- Nuclear weapons and the United States
- Nuclear weapons of Russia
- Nuclear weapons of People's Republic of China
- Nuclear weapons of India
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