BEIJING - Mao Zedong famously dismissed the atomic bomb as a "paper tiger," able to kill and terrify, but not decisive in war. Even so, China built a nuclear arsenal of its own, and now concerns about the effectiveness of that arsenal as a deterrent are driving it intoconfrontation with the United States over an anti-missile system being built in South Korea . Here's an explanation of why.
How big is China's nuclear arsenal?
China conducted its first nuclear test in 1964, and has developed a stable of nuclear missiles. But it is not a big stable, compared with the thousands of warheads held by the United States and Russia.
China does not reveal the size of its nuclear forces. It has about 260 nuclear warheads that could be put on missiles, and by the Pentagon's latest estimate, China has between 75 and 100 intercontinental ballistic missiles. Some estimates are lower, and one recent assessment said 40 to 50 of China's ballistic missiles could reach the continental United States.
The United States has deployed about 1,370 nuclear warheads and has stockpiled more than 6,500, and has submarines and aircraft able to launch nuclear weapons.
China has also built several submarines that can launch nuclear missiles. But even its latest-model submarine "is noisy and quite vulnerable to anti-submarine warfare," and therefore is not a very potent addition to its nuclear deterrent, M Taylor Fravel, a professor at the Massachusetts Institute of Technology, and Fiona S Cunningham, a graduate student there, who recently published an assessment of China's nuclear modernization, said by email.
China has also been upgrading some of its missiles so that several nuclear warheads can be placed on a single missile that then unleashes them on different targets.
China has had the ability to put multiple warheads on missiles since the 1990s, but seems to have done so only recently, when some missiles were installed with three or four warheads, said Jeffrey Lewis, an expert on China's nuclear forces at the Middlebury Institute of International Studies. This showed how China has been cautious in playing catch-up to the United States, he said.
"I don't think that the Chinese and US have, historically, experienced the kind of tit-for-tat modernization that we saw during the US-Soviet arms race," Lewis said. "The Chinese more or less modernized for their own reasons and according to their own ideas."
Why has China's nuclear arsenal stayed relatively small?
By the time China joined the nuclear club, the United States and Russia were well ahead in building a stockpile of weapons. Mao decided to stick to a relatively small arsenal big enough to serve as a deterrent, and that decision was made a fait accompli by the political turmoil of Mao's era, which held back the nuclear weapons program.
"China's leaders thought that the important thing was to master the technology," Lewis said. "While the United States did fine calculations of the deterrence balance, Chinese leaders tended to think of deterrence like a checklist of achievements."
Ever since, Chinese nuclear doctrine has stuck to the idea of a "minimum means of reprisal," with a force designed to survive and retaliate after an initial nuclear attack. Alongside that, China has a nuclear "no first use" policy: that it will not be the first to launch nuclear weapons against another nuclear foe, and that it will not use its nuclear weapons against a country without nuclear weapons.
Even so, China has been expanding and upgrading its nuclear forces, and that modernization may speed up if the government feels that it is falling too far behind the United States.
"China is probably confident in its ability to be able to retaliate, but given the size and sophistication of US nuclear forces and the steady development of ballistic missile defenses, coupled with China's small nuclear arsenal, the margin for error is thin," Fravel and Cunningham said.