China's nuclear forces are fuel for controversy. Beijing is modernizing two legs of its nuclear triad—land- and sea-based ballistic missiles—with new weapons built and stored underground. It is also moving to solid-fueled weapons that can be launched in minutes from liquid-fueled missiles and to mobile land-based missiles from silos. More of these missiles will have the ability to reach the U.S. In addition, China is modernizing its nuclear warheads, despite having ceased explosive nuclear tests in 1996.

But China's nuclear forces, controlled by the Second Artillery Corps of the People's Liberation Army, still number slightly under 200 armed missiles, much less than the U.S. or Russia. Though it is the only one of the five nuclear-weapons state signatories to the nuclear Nonproliferation Treaty that is expanding its arsenal, there is no evidence to suggest it is building, or has built, hundreds or thousands of new nuclear warheads, despite claims by some Western observers. Evidence does suggest, however, that China's nuclear forces remain focused on ensuring a nuclear deterrent through the ability to deliver a devastating second strike against enemy cities.

According to estimates of the Federation of American Scientists (FAS), released this month, China has about 60 ICBMs with range of at least 5,500 km (3,400 mi.). Of these, about 32 are older, silo-based, liquid-fueled DF-4 and DF-5A missiles, while about 28 are road-mobile DF-31 and DF-31A solid-fueled missiles, deployed starting in 2006 and 2007, respectively. In addition to ICBMs, the FAS estimates that China retains about eight old liquid-fueled DF-3As with 3,000-km range and 80 or so 2,150-km-range DF-21s.

There is no indication that a road-mobile missile with multiple independently targetable (Mirv) warheads—sometimes called the DF-41—has been deployed, says Hans Kristensen of the FAS, although its carrier vehicle has been sighted. “The estimate of the U.S. intelligence community is that all of China's ballistic missiles are single-warhead,” Kristensen says. Adding multiple warheads sacrifices range, which is not worthwhile if China wants to hold cities such as Washington at risk, he notes. It is more likely that China might equip missiles with one warhead and several decoys, he says. Michael Chase of the Rand Corp. agrees that “the DF-41 is not out there yet.”

The FAS estimates are in line with the annual U.S. Defense Department report to Congress on China's military forces, released in May, which calculates that China has 50-75 ICBMs and states that a DF-41-class weapon is not yet operational. “China may also be developing a new road-mobile ICBM, possibly capable of carrying Mirvs,” the report states.

The new road-mobile missiles are stored in tunnels, in what is sometimes called the “Underground Great Wall.” “They bury everything,” notes Ian Easton of the Project 2049 Institute, a U.S. think tank. “You can't count the number of bombers China has, or the number of fighters. For a good portion of the time, they're underground.” The 2013 Pentagon report states that the effort to bury military facilities “took on a renewed urgency following China's observation of U.S. and NATO air operations in Operation Allied Force and of U.S. military capabilities during the 1991 [Persian] Gulf War.”

Kristensen describes the Chinese land-based forces, with the massive underground fortifications that exist, as “submarines on wheels.” As Benjamin Purser and Chase note in an August 2012 Jamestown Foundation report on the Jin, it is estimated by the U.S. Office of Naval Intelligence to be “somewhat noisier than Russia's older Delta II SSBNs.” This means the Chinese navy cannot use submarines as other nations do—as a sustained deterrent that can disappear in a wide geographic area. Tunneling on land is a way to duplicate this capability within China's technical means.

But there is “no correlation” between underground facilities and the size of China's nuclear arsenal, Easton points out. “You can't say you've got hundreds of thousands of miles of tunnels and thus, you must have X number of warheads or X number of vehicles,” he notes. “There's just no evidence that would suggest that. It just shows that you've invested greatly in redundancy, in protection capabilities.”

Easton says that because the tunnels are poorly ventilated, even after a short time underground, soldiers “start to get physically sick because of the exhaust fumes.” The Chinese might keep missiles and warheads underground, he says, but not people. So, it is possible to estimate the number of missiles by examining above-ground facilities near bunkers, he asserts. The official Pentagon estimates are in part driven by such estimates, says Jeffrey Lewis of the James Martin Center for Nonproliferation Studies at the Monterey (Calif.) Institute for International Studies. “They can't see the launchers. What they see is the force structure, infer the number of launchers,” he says.

According to Easton, China keeps warheads separate from delivery systems. The country's central nuclear warhead storage facility is south of Baoji in Shaanxi Province, near the geographical center of China, according to a July 2013 report by Easton and Mark Stokes, also of the Project 2049 Institute. Aside from the central facility, a “small handful of warheads” are maintained at six regional storage facilities, each subordinate to a missile base, Stokes notes in a 2010 report.

While satellite imagery has revealed a “significant expansion of Second Artillery's missile brigade infrastructure” over the last several decades, according to Easton and Stokes, a review of the “nuclear warhead storage and handling system offers no obvious signs of a significant increase in China's nuclear stockpile.” The researchers conclude that the Second Artillery is growing to accommodate new non-nuclear missiles.

China's sea-based deterrent force remains minimal, the FAS and Pentagon agree. A single Xia-class submarine entered service in 1986, but it is not considered to be operational—it never returned to sea after a “lengthy shipyard overhaul in 2005-06,” the FAS says. The Chinese have three operational Jin-class SSBNs and may be building two more, the Pentagon report states. Each submarine can carry up to 12 JL-2 missiles, but Kristensen points out that “they do not take warheads on patrol. This sub force is not fully operational yet. It might become operational this year or next year. ”

Whether China “will conduct routine peace-time deterrence patrols with nuclear weapons” remains an open question, write Chase and Purser in their 2012 report. The Second Artillery offers the political leadership, “great transparency and constant control,” they assert. “In the current political environment, the inability for civilian leaders to remain constantly informed—and in control—of SSBN operations may push them beyond their comfort zone, if Beijing maintains routine deterrent patrols.”

The third leg of China's nuclear triad remains minimal. Kristensen estimates that the country has around 40 weapons tasked to H-6 bombers and fighters with a secondary nuclear mission. These warheads have yields ranging from 10 kilotons to 3 megatons. Hui Zhang of the Belfer Center for Science and International Affairs at Harvard University says the number is around half that.

The DH-10 land-based cruise missile was deployed starting in about 2006, according to the 2013 FAS report, which estimates that there are around 250 launchers. Dennis Gormley, of the Ridgway Center for International Security Studies at the University of Pittsburgh, says the DH-10 is closely modeled on the Russian KH-555. He believes there are 3-5 “reloads” per cruise missile launcher, but he adds, “I think they are all conventional. I don't see China turning to cruise missiles for nuclear [weapons].”

Zhang estimates that China has stockpiles of 12-20 tons of highly enriched uranium (HEU) and 1.3-2.3 tons of plutonium available for weapons. Since the country stopped producing HEU in 1987 and plutonium around 1990, he believes it could build at most 1,000 nuclear weapons.

However, judging from other nuclear weapons states that release more information about their nuclear arsenals (China releases no official numbers on the size of its arsenal, and the Chinese embassy in Washington did not respond to a request for comment), usually no more than half of a stockpile can be used in weapons at any given time. Therefore, Zhang sets the realistic maximum for China at 500 weapons, but he estimates the total number of weapons in the nation's stockpile is smaller, about 170 warheads.

Phillip Karber, president of the Potomac Institute for Policy Studies, cites larger figures from Gen. (ret.) Viktor Yesin, a former commander of the Russian strategic rocket forces. But Zhang says Yesin's estimates are “based on a lot of mistakes,” and notes that Yesin says HEU production continued for years at facilities that had been verified as closed. “[Yesin] assumes that their plutonium reactor continues running,” Zhang says. “But, in fact, they already shut down in 1984. This is easy to monitor by satellite imagery, at Jiquan. If it's running during the winter, it is very easy to see the water vapor.”

Chase notes that “the Chinese still don't care about parity. They care about having a credible retaliatory capability.” U.S. missile-defense efforts diminish that capability, he adds, which may explain the slight buildup of Chinese ICBMs.

Chinese missile number estimates are drastically undercounted, according to Karber, because they do not include reloads. Kristensen says reloads are possible in principle, and that the DF-21, a regional missile, is indeed likely to have several reloads for each conventional launcher; he adds that reloads on nuclear ICBMs do not make tactical sense. In a “shooting situation,” launchers could not be expected to survive very long after they lofted their missiles.

But, the equation is different for conventional forces. “They really see their conventional capabilities for countering U.S. intervention as the main deterrent for us getting involved in a conflict with China,” says Chase. Kristensen agrees: “That's what they are doing, equipping the Second Artillery Corps with medium-range conventional missiles.”

“A somewhat larger and definitely more survivable nuclear force is what they need for their deterrent to remain credible in the near-to-mid-term, so I do expect them to continue building up their force.” Chase says. “They will have a larger nuclear force than they have today five years from now or 10 years from now, but I don't see it as being on par with what the U.S. or Russians will have.”