[国际新闻] 美国核武越强中美更易开战

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七月出刊的《大西洋月刊》登出两名战略专家利贝（K.A. Lieber）和普里斯（D.G. Press）合撰的长文，标题是〈美国的核武优越情结：何以美国成长中的核武霸权很可能诱发对华开战〉，二人只是基于美国自身的利益为文，并非挑衅而是警告。人在德国社区" G; j' f+ m0 F# d, q
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美自恃核武绝对优势
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利、普二人的长文一上来就说，由于美国近十多年来在核武研发投入大量人力物力，冷战时代美苏「互相保证毁灭」的恐怖平衡早已被抛弃，因为美国的核武优势在今天的中美关系上形成极大的不平衡。估计北京仅有七十到八十个可操控的核子弹头，可由东风五型长程洲际导弹发射，但操作缓慢，其他如潜艇等也很落伍。目前中国的国际地位正在上升，但美国的核武优势却快速增加，以往如要销毁北京的核子武库必然引起大量伤亡，今天因各种技术的改善，情况大变，中国的核武很易受到攻击，也因此让美国在核武战术上有更多选择。人在德国社区$ L) y) N( w% D% m5 s1 x

　　美国虽未必正在采取发动第一击的核武战略，但却以之追求三大目的：阻止传统或核武战争的发生；在危机爆发时，作为牵制核武敌国的手段；及在险恶环境之下，对使用核武有较好的选择。 ) _% l/ _  u) K$ W

　　在美国绝对优势之下，中国遭受核武第一击之后并无反击的能力。根据已解密的资料，中国共有十八座地下核弹发射坑。针对河北的洲际飞弹，过去一段时期，美国为了作先发制人的核武攻击，在太平洋至少维持两艘核武潜艇经常警戒，于接获命令十五分钟之内，可用二十四枚载有核武弹头的三叉戟二型飞弹把发射坑道毁灭。
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　　今天的情况更是不同，不仅一枚飞弹可载多枚预设目标的弹头，并且精准性大为提高。按美国某些专家二○○六年的评估，尽管中国的飞弹发射基地多在人口较少的地区，但辐射尘等带来的灾害，估计仍会使数百哩地区的平民死亡高达三百多万！就因为今天美国的核武研发突飞猛进，可以选择爆炸时当量较小的核武弹头，加上卫星定位精确系统。有人估计击毁中国的某一飞弹发射坑，可能只引起数百人到六千人左右的伤亡。基于这一假设，美国领袖很可能在附庸国之类的怂恿下，由于具有核武绝对优势情绪的诱使，以致冒然对中国发动先发制人的核武突袭。 ! L- H' T1 s$ |& I1 L

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　　再以台海局势为例，利、普二人认为如果台湾宣布独立，北京必然采取行动，否则不仅永远丧失台湾，很可能政权亦因此不保，故会将核武进入警戒状况，届时美国如何回应？如果北京并不缩手，而战事已经爆发，美国凭借其核武优势，传达讯息迫使北京撤销其核武的备战状况，把战火停留在传统武器层面；但如北京有意以核武攻击邻近的海外地区，则美国可能采取先发制人的攻击。但此举危险性极大，万一北京的洲际飞弹发射坑有一个成为漏网之鱼，对美国而言其后果不堪设想。更何况北京还有六十枚左右的中短程核子飞弹，可以用来报复美军及其盟友。

　　因此，说到底，利、普二氏认为美国的核武优势有如一剑双刃，既可解决问题，也可以制造问题，争论极多。它是一张可以保护盟友和压制敌人的王牌，也可能引发新的军备竞争和带来新的危险，无论是美国及其敌友都无法承受，而首当其冲的则是因为台海危局引发的中美关系，届时如何是了？8 Z& b+ Q. A( r7 A

Why America's Growing Nuclear Supremacy May Make War With China More Likely. ~+ p9 R( l4 U+ W% h
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by Keir A. Lieber and Daryl G. Press rs238848.rs.hosteurope.de8 {- L9 [& C" ^1 S/ R
In the coming years, as China's economy booms and its armed forces grow, the United States will seek to curb Chinese military power and influence. The U.S.-China rivalry is poised to become the world's most dangerous strategic relationship. Optimists might contend that the pacifying effects of economic integration will forestall outright hostility and conflict between Washington and Beijing. Others would argue that the strategic competition itself augurs peace and stability between the superpowers, because each country's ar-senal of nuclear weapons constitutes a security blanket: Just as the danger of mutual nuclear annihilation—or mutual assured destruction (MAD), as it was labeled then—helped prevent war between the United States and the Soviet Union during the Cold War, so too will nuclear deterrence cool tensions between the United States and China.
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But little about the emerging nuclear balance between the United States and China should lead anyone to assume a similar stabilizing effect. The United States is pursuing capabilities that are rendering MAD obsolete, and the resulting nuclear imbalance of power could dramatically exacerbate America's rivalry with China. % I3 k) G$ g. m7 X& H  i

In the 1990s, with the Cold War receding, nuclear weapons appeared to be relics. Russian and Chinese leaders apparently thought so. Russia allowed its arsenal to decline precipitously, and China showed little interest in modernizing its nuclear weapons. The small strategic force that China built and deployed in the 1970s and early 1980s is essentially the same one it has today.
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But meanwhile, the United States steadily improved its "counterforce" capabilities—those nuclear weapons most effective at targeting an enemy's nuclear arsenal. Even as it reduced the number of weapons in its nuclear arsenal, the U.S. made its remaining weapons more lethal and accurate. The result today is a global nuclear imbalance unseen in 50 years. And nowhere is U.S. nuclear primacy clearer—or potentially more important—than in the Sino-U.S. relationship.

China has approximately 80 operationally deployed nuclear warheads, but only a few of them—those assigned to single-warhead DF-5 intercontinental ballistic missiles (ICBMs)—can reach the continental United States. (There is no definitive, unclassified count of China's DF-5 ICBMs, but official U.S. statements have put the number at 18.) China has neither modern nuclear ballistic-missile submarines nor long-range nuclear bombers. Moreover, China's ICBMs can't be quickly launched; the warheads are stored separately, and the missiles are kept unfueled. (Unlike the solid fuel used in U.S. missiles, the liquid fuel used to propel Chinese ICBMs is highly corrosive.) Finally, China lacks an advanced early-warning system that would give Beijing reliable notice of an incoming attack.
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This small arsenal fulfilled China's strategic requirements in the 20th century, but it is now obsolete. The current Chinese force was designed for a different era:when China was a poor nation with a limited role on the world stage, and when U.S. and Soviet missiles were too inaccurate to carry out a disarming strike—even against Beijing's small force. But China's international presence is expanding, and America's counterforce capabilities have soared. Moreover, one of the biggest constraints that would deter American leaders from contemplating a disarming strike is fading away. In the past, a U.S. preemptive attack would have generated horrific civilian casualties, but that may soon cease to be the case.
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How the United States achieved nuclear dominance after the Soviet Union collapsed is an open secret. The Navy refitted its entire fleet of nuclear-armed submarines with new, highly accurate Trident II missiles and replaced many of the 100-kiloton W76 warheads on these missiles with 455-kiloton W88 warheads. (One kiloton is the explosive energy released by 1,000 tons of TNT.) The result is an unprecedented combination of accuracy and destructive power, essential for an attack on hardened silos. The Navy also recently tested a GPS guidance system that would dramatically boost the accuracy, and thus lethality, of the submarine missile arsenal...

From a military perspective, this modernization has paid off: A U.S. nuclear first strike could quickly destroy China's strategic nuclear arsenal. Whether launched in peacetime or during a crisis, a preemptive strike would likely leave China with no means of nuclear retaliation against American territory. And given the trends in both arsenals, China may live under the shadow of U.S. nuclear primacy for years to come.

This assessment is based on unclassified information, standard targeting principles, and formulas that defense analysts have used for decades. (And we systematically chose conservative estimates for key unknowns, meaning that our analysis understates U.S. counterforce capabilities.) The simplest version of an American preemptive strike would have nuclear-armed submarines in the Pacific launch Trident II missiles at the Chinese ICBM field in Henan province. The Navy keeps at least two of these submarines on "hard alert" in the Pacific at all times, meaning they're ready to fire within 15 minutes of a launch order. Since each submarine carries 24 nuclear-tipped missiles with an average of six warheads per missile, commanders have almost 300 warheads ready for immediate use. This is more than enough to assign multiple warheads to each of the 18 Chinese silos. Chinese leaders would have little or no warning of the attack.   f' {2 d+ D! v9 \2 ?; c5 m4 G7 u7 l
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During the Cold War, U.S. submarines posed little danger to China's silos, or to any other hardened targets. Each warhead on the Trident I missiles had little chance—roughly 12 percent—of success. Not only were those missiles inaccurate, their warheads had a relatively small yield. (Similarly, until the late 1980s, U.S. ICBMs lacked the accuracy to carry out a reliable disarming attack against China.) But the Navy's new warheads and missiles are far more lethal. A Trident II missile is so accurate, and the newer W88 warhead so powerful, that if the warhead and missile function normally, the destruction of the silo is virtually assured (the likelihood is calculated as greater than 99 percent).
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In reality, American planners could not assume such near-perfect results. Some missiles or warheads could malfunction: One missile's rockets might fail to ignite; another's guidance system might be defective. So a realistic counterforce plan might assign four warheads to each silo. The U.S. would "cross-target" the missiles, meaning that the warheads on each missile would each go to different silos, so that a silo would be spared only if many missiles malfunctioned. Even assuming that 20 percent of missiles malfunctioned—the standard, conservative assumption typically used by nuclear analysts—there is a 97 percent chance that every Chinese DF-5 silo would be destroyed in a 4-on-1 attack. (By comparison, a similar attack using Cold War–era Trident I missiles would have produced less than a 1 percent chance of success. The leap in American counterforce capabilities since the end of the Cold War is staggering.)

Beyond bolstering the ability to conduct a first strike, the improvements to U.S. counterforce weapons also allow war planners to design nuclear options that will make the weapons more "usable" during high-stakes crises. Nuclear planners face many choices when they consider striking a given target. First, they must choose a warhead yield. The American arsenal includes low-yield weapons such as the B-61 bomb, which can detonate with as little explosive force as 0.3 kilotons (one-fiftieth the power of the bomb that destroyed Hiroshima), and high-yield weapons such as the B-83 bomb, which can yield 1,200 kilotons (80 times the strength of the Hiroshima bomb). For a military planner, high-yield weapons are attractive because they're very likely to destroy the target—even if the weapon misses by some distance. Low-yield warheads, on the other hand, can be more discriminating, if planners want to minimize civilian casualties.

A second key decision for war planners is whether to set the weapon to detonate at ground level or in the air above the target. A groundburst creates enormous overpressure and ground shock, ideal for destroying a hardened target. But groundbursts also create a lot of radioactive fallout. Dirt and other matter is sucked up into the mushroom cloud, mixes with radioactive material, and, after being carried by the wind, falls to earth in the hours after the blast, spreading lethal radiation. $ o/ _2 P, _" f' f* }. p" X* |
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Airbursts create smaller zones of extremely high overpressure, but they also generate very little fallout. If the detonation occurs above a threshold altitude (which depends on the weapon yield), virtually no heavy particles from the ground mix with the radioactive material in the fireball. The radioactive material rises into the high atmosphere and then falls to earth over the course of several weeks in a far less dangerous state and over a very wide area, greatly reducing the harm to civilians. 9 Y* E  l: B/ I( w; @/ t
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In the past, a nuclear attack on China's arsenal would have had horrific humanitarian consequences. The weapons were less accurate, so an effective strike would have required multiple high-yield warheads, detonating on the ground, against each target. The Federation of American Scientists and the Natural Resources Defense Council modeled the consequences of such an attack—similar to the submarine attack described above—and published their findings in 2006. The results were sobering. Although China's long-range missiles are deployed in a lightly populated region, lethal fallout from an attack would travel hundreds of miles and kill more than 3 million Chinese civilians. American leaders might have contemplated such a strike, but only in the most dire circumstances.
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But things are changing radically. Improved accuracy now allows war planners to target hardened sites with low-yield warheads and even airbursts. And the United States is pushing its breakthroughs in accuracy even further. For example, for many years America has used global-positioning systems in conjunction with onboard inertial-guidance systems to improve the accuracy of its conventionally armed (that is, nonnuclear) cruise missiles. Although an adversary may jam the GPS signal near likely targets, the cruise missiles use GPS along their flight route and then—if they lose the signal—use their backup inertial-guidance system for the final few kilometers. This approach has dramatically improved a cruise missile's accuracy and could be applied to nuclear-armed cruise missiles as well. The United States is deploying jam- resistant GPS receivers on other weapons, experimenting with GPS on its nuclear-armed ballistic missiles, and planning to deploy a new generation of GPS satellites—with higher-powered signals to complicate jamming. / }' n( L, |" z" r( C; W2 ?) b- y
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The payoff for equipping cruise missiles (or nuclear bombs) with GPS is clear when one estimates the civilian casualties from a lower-yield, airburst attack. We asked Matthew McKinzie, a scientific consultant to the Natural Resources Defense Council and coauthor of the 2006 study, to rerun the analysis using low-yield detonations compatible with nuclear weapons currently in the U.S. arsenal. Using three warheads per target to increase the odds of destroying every silo, the model predicts fewer than 1,000 Chinese casualties from fallout. In some low-yield scenarios, fewer than 100 Chinese would be killed or injured from fallout. The model is better suited to predicting fallout casualties than to forecasting deaths from the blast and fire, but given the low population in the rural region where the silos are, Chinese fatalities would be fewer than 6,000 in even the most destructive scenario we modeled. And in the future, there may be reliable nonnuclear options for destroying Chinese silos. Freed from the burden of killing millions, a U.S. president staring at the threat of a Chinese nuclear attack on U.S. forces, allies, or territory might be more inclined to choose preemptive action.! V9 _- V  b$ T9 H3 I% G9 g) I
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STRATEGIC IMPLICATIONS OF THE NUCLEAR IMBALANCE 人在德国社区4 h' _/ K; l. |: U4 T

The most plausible flash point for a serious U.S.-China conflict is Taiwan. Suppose Taiwan declared independence. China has repeatedly warned that such a move would provoke an attack, probably a major air and naval campaign to shatter Taiwan's defenses and leave the island vulnerable to conquest. If the United States decided to defend Taiwan, American forces would likely thwart China's offensive, since aerial and naval warfare are strengths of the U.S. military. But looming defeat would place great pressure on China's leaders. Losing the war might mean permanently losing Taiwan. This would undermine the domestic legitimacy of the Chinese Communist Party, which increasingly relies on the appeal of nationalism to justify its rule. A crippling defeat would also strain relations between political leaders in Beijing and the Chinese military. To stave off a regime-threatening disaster, the political leaders might decide to raise the stakes by placing part of the Chinese nuclear force on alert in hopes of coercing the United States into accepting a negotiated solution (for example, a return to Taiwan's pre-declaration status). 人在德国社区5 i* k. i+ Q8 T$ F5 n

By putting its nuclear forces on alert, however, China's leaders would compel a U.S. president to make a very difficult decision: to accede to blackmail (by agreeing to a cease-fire and pressuring the Taiwanese to renounce independence), to assume that the threat is a bluff (a dangerous proposition, given that each Chinese ICBM carries a city-busting 4,000-kiloton warhead), or to strike the Chinese missiles before they could be launched.

How do America's growing counterforce capabilities affect this scenario? First, American nuclear primacy may prevent such a war in the first place. China's leaders understand that their military now has little hope of defeating U.S. air and naval forces. If they also recognize that their nuclear arsenal is vulnerable—and that placing it on alert might trigger a preemptive strike—the leaders may conclude that war is a no-win proposition.   A( i2 c& \) P- O' f

Second, if a war over Taiwan started anyway, U.S. nuclear primacy might help contain the fighting at the conventional level. Early in the crisis, Washington could quietly convey to Beijing that the United States would act decisively if China put its vulnerable nuclear arsenal on alert. rs238848.rs.hosteurope.de: ?2 t( q" n; e( m9 y# G! S# T
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Finally, if China threatened to launch nuclear attacks against America's allies, its territory, or its forces in Asia, nuclear primacy would make a preemptive first strike more palatable to U.S. leaders. Any decision to attack China's ICBM force, though, would be fraught with danger. A missile silo might have escaped detection. Furthermore, a strike on China's 18 ICBMs would leave Beijing with roughly 60 shorter-range nuclear missiles with which to retaliate against U.S. forces and allies in the region. However, in the aftermath of a "clean" disarming strike—one that killed relatively few Chinese—American leaders could credibly warn that a Chinese nuclear response would trigger truly devastating consequences, meaning nuclear attacks against a broader target set, including military, government, and possibly even urban centers. In light of warnings from Chinese defense analysts and from within China's military that it might use nuclear weapons to avoid losing Taiwan, an American president might feel compelled to strike first. In this terrible circumstance, he or she would reap the benefits of the past decade's counterforce upgrades.& ~+ J8 p$ L$ u: [' G4 _/ M

[ 本帖最后由日月光于 2007-7-5 13:29 编辑 ]

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