It is estimated that the current stockpile has 215 warheads, 60 of which are in reserve.
The UK Trident program encompasses the development, procurement, and operation of the current generation of British nuclear weapons as well as a means to deliver them. Trident is an operational system of four Vanguard-class submarines armed with Trident II D-5 ballistic missiles, able to deliver thermonuclear warheads. Only one British submarine will patrol at any given time, carrying 48 warheads. The submarine patrols at a reduced state of alert - capable of firing its missiles within several days instead of within several minutes. Britain maintains fewer than 200 operationally available warheads.
The weapons are configured flexibly in order to obtain a low yield for "sub-strategic missions" or higher yields for strategic missions.
The number of weapons in China’s nuclear arsenal is slowly growing. China has approximately 250 warheads in its stockpile for delivery by nearly 250 land-based ballistic missiles, aircraft, and submarine fleet.
Bombers: China's bomber force is reportedly antiquated based on Chinese-made versions of outdated Soviet aircraft. A supersonic fighter-bomber currently being developed is not believed to have a nuclear mission.
Ballistic Missiles: China uses liquid fuelled missiles which would take some time to prepare for launch, and reportedly stores the warheads separate from these missiles. However, such missiles are slowly being replaced by a solid fueled missile, the DF-3, as well as accurate road-mobile missiles. Each missile carries one warhead. It is estimated that China’s current arsenal includes 60 long-range missiles that can reach the United States.
Non-strategic warheads: There is no official evidence of existence of non-strategic weapons. However, the US Defense Intelligence Agency believes that China has developed nuclear artillery, demolition munitions and nuclear capable short-range missiles. Land attack cruise missiles currently under development might be nuclear capable.
Warheads: China's strategic weapons have high yields - mostly in the megaton range - but are not as accurate as those of the US or Russia. It is believed that China has developed a neutron bomb.
In 2008, France announced further reductions in its nuclear arsenal to fewer than 300 warheads, bringing the arsenal to its lowest possible number while still meeting strategic requirements.
Bombers: Both the Navy and Airforce deploy nuclear capable aircraft. France has three land-based squadrons and one sea-based flotilla assigned to the aircraft carrier Charles de Gaulle.
Submarines: France has four nuclear capable submarines, three of the Triomphant class. The last Redoubtable class, the L’Inflexible, was decommissioned in 2008.At least one French submarine is at sea at any given time.
France dismantled its 18 intermediate range missiles from 1996-98. The nuclear testing facilities at Moruroa and Fangataufa were closed following France's accession to the CTBT. France ceased production of plutonium and highly enriched uranium in 1992 and 1996 respectively. In the absence of full-scale nuclear testing, France established a simulation program to guarantee that its nuclear warheads will perform to their design specifications.
As of early 2015, it is estimated that the US Defense Department maintains about 4,700 nuclear warheads. Approximately 180 warheads are deployed nonstrategic and 1,900 are deployed strategic while 2,620 warheads are in reserve. The total US inventory is roughly 7,200 warheads.
Under New START, the US and Russia report the size of their nuclear arsenals every six months.
Intercontinental ballistic missiles: The US has four types of intercontinental ballistic missiles currently in use: Minuteman II, Minuteman III, Peacekeeper, and Midgetman.
Submarine launched ballistic missiles: All of the US Navy’s 14 Ohio-class nuclear-powered ballistic missile submarines carry Trident II ballistic missiles. Normally, 12 of these submarines are considered operational at any given time. Starting in 2015, the number of missile tubes on each will be reduced from 24 to 20.
Bombers: Long-range bombers are equipped with air launched cruise missiles and free fall bombs. The B-2 bomber is capable of carrying the B61-11, an earth-penetrating nuclear bomb, introduced in November 1997. The US is continuing to produce nuclear capable advanced cruise missiles (ACM). Also, the US is planning a new bomber, known as the long-range strike bomber to begin replacing existing bombers beginning in the mid-2020s.
Non-strategic forces: Nuclear weapons were removed from surface ships in 1991. However, the US maintains a robust stockpile of tactical nuclear weapons in Belgium, Germany, Italy, the Netherlands and Turkey through a NATO nuclear sharing agreement and is not expected to reduce these while Russia maintains a large stockpile.
In addition to the active stockpile, the U.S. maintains a large inactive stockpile as a "hedge" in case arms control expectations fail to materialize.
Russia is modernizing its strategic and nonstrategic nuclear warheads. It currently has a total inventory of 7,500 warheads. Of these, 1,780 are deployed strategic and 2,720 are in reserve.
Intercontinental ballistic missiles: Russia is continuing to test and modernize its SS-27 missile.
Submarines: Russia has reduced its operational nuclear submarines from 62 in 1990 to 17 in 2001. All Delta I and Delta II subs have been withdrawn from service. Russia continues to produce SS-N-23 SLBMs to keep the Delta IVs in service.
Non-strategic forces: Russia agreed to remove tactical nuclear weapons from surface ships in 1991, but there is no confirmation that this has happened. Russia keeps a large stockpile of additional tactical weapons in regional storage sites. There has been a strong call from sectors of the government and military to increase reliance on tactical weapons in response to NATO's eastward expansion and to offset NATO's superior conventional forces. In addition, Russia is also updating some of its nonstrategic forces, phasing out its Soviet-era weapons and replacing them with newer but fewer weapons.
Israel neither acknowledges nor denies that it has nuclear weapons. Israel is generally regarded as a de facto nuclear weapon state. Mordechai Vanunu, a former nuclear technician at the Dimona facility, revealed that Israel could have up to 200 nuclear warheads (Revealed: The Secrets of Israel's Nuclear Arsenal, Sunday Times, London, October 5, 1986). Vanunu also reported that Israel had produced tritium and lithium, indicating that Israel may have developed boosted nuclear weapons. Seymour Hersh has claimed that Israel has developed low-yield weapons for artillery and land-mines, as well as thermo-nuclear weapons (The Sansom Option, Random House, New York, 1991). Some analysts assume that Israel could not have advanced to the point of producing thermonuclear weapons because they are not known to have conducted any physical nuclear testing. However, it is reported that Israel has been able to acquire data on thermonuclear tests from France and the U.S. Also, there is speculation that a signal detected by a US satellite over the Atlantic on September 22, 1979 was in fact a nuclear test conducted by either Israel or South Africa.
Israel currently deploys two nuclear capable ballistic missile systems: the Jericho I (range 660 km) and the Jericho II (range 1500 km). In addition, the Shavit space launch vehicle could be modified to carry nuclear weapons giving it an intercontinental capability (range 7800 km).
It is estimated that Israel has a total nuclear stockpile of 80 nuclear weapons.
India demonstrated a nuclear weapons capability in 1974 by detonating a device in what it called a peaceful nuclear experiment. Then in May 1998, India openly tested nuclear weapons and declared itself a nuclear weapons power. India has enough separated weapons grade plutonium to make about 85 nuclear warheads.
India is estimated to have produced approximately 52 kilograms of weapons-grade plutonium, sufficient for 100-130 nuclear warheads. Based on available information, it is estimated that India has produced 90-110 nuclear warheads.
Land-based missiles: India has developed three missiles which could be adapted to nuclear capability. They are the Prithvi (range 200 km), the short-range Agni I, and the medium-range Agni II. India has also been enhancing its nuclear air-delivery capability by purchasing and re-producing the Russian Su-30MK fighter-bomber.
Naval: India has developed two naval nuclear weapons systems: a nuclear-powered ballistic missile submarine and a ship-launched ballistic missile.
Aircraft: India has the fourth-largest air force in the world. India is updating its 51 Mirage 2000H aircraft, which is scheduled for completion by mid-2020.
Pakistan is believed to have started developing its nuclear weapons program in 1971, following its war with India. By1998, it was believed that Pakistan had built a small arsenal of unassembled nuclear weapons. In response to the Indian tests of May 1998, Pakistan followed with nuclear tests itself in Chagai Hills. It is now possible that Pakistan would have built and assembled up to 100-120 nuclear warheads.
Pakistan possesses about 30 nuclear capable surface-to-surface missiles provided by China. Pakistan has built and tested its own ballistic missiles including the Haft-3 (range 600 km) and the Ghauri (range 1500 km).
Pakistan is currently in the process of building two new plutonium production reactors and a new reprocessing facility to fabricate more nuclear weapons fuel. Also, Pakistan is developing new delivery systems. It is estimated that if the expansion of the country continues, Pakistan’s nuclear weapons stockpile could reach 150-200 warheads in a decade.
Ballistic missiles: Pakistan has three operational nuclear-capable ballistic missiles: the short-range Ghaznavi and Shaheen-I, and the medium-range Ghauri. There are at least three other nuclear ballistic missiles under development, the medium-range Shaheen-2 and the short-range Abdali and Nasr.
Cruise missiles: Pakistan is developing two new cruise missiles, the Babur and Ra’ad.