经过一个联合工作小组数月的评估，美国国防部近日宣布，驻韩美军司令部将在韩国部署末段高空区域防御系统（“萨德”），作为“保障韩国及韩国人民安全的防御措施，同时防止盟军部队受朝鲜大规模杀伤性武器和弹道导弹的威胁。”

“萨德”反导系统资料图（选自：国际在线）

这一决定已经迟到了好几年。其间，华盛顿和首尔想通过外交和制裁，包括与中俄合作，来阻止朝鲜发展核武器和导弹，但这一努力以失败告终。今年年初以来，朝鲜试爆了被它称为氢弹的第四个核装置，并试射了多枚各种射程的导弹，包括几周前的“舞水端（化城-10）”中程弹道导弹。“舞水端”射高可达1400公里，射程3500公里，飞行包线超过了韩国导弹防御系统（KAMD）短、中程弹道导弹的有限拦截能力。

美国国防部的声明强调，新“萨德”系统“只针对朝鲜核武器和导弹威胁，不会针对任何第三国”。然而，俄罗斯和中国政府以种种理由对这一决定展开抨击。

例如，俄罗斯副外长伊戈尔·莫古洛夫指责“美国在亚太建立全球反导能力，试图改变现有力量平衡”。他声称，此举将“不可避免地导致东北亚紧张局势升级，妨碍去核化等朝鲜半岛问题的解决。”

中国外交部更进一步要求美国和韩国“中止”部署“萨德”。发言人陆慷称此举完全是出于“一己私利”，认为部署“萨德”将威胁和平与稳定，使朝鲜半岛紧张局势升级，“严重破坏地区战略平衡，损害包括中国在内的域内国家的战略安全利益”。

美国国务院发言人约翰·柯比表示，美国已经“聆听（中国人的）关切，并向他们提供了这一系统工作方式的情况通报”。美国官方也向俄罗斯提供了同样的通报。然而，通报没有收到什么效果，因为俄中两国参与对话的人员对前来通报情况的人及相关信息并不信任。不管怎样，他们反对美国弹道导弹防御系统（BMD）主要是着眼于地缘政治，而非技术考量。

的确，俄中两国军事策略家们可以假设导弹防制系统如何帮助美国对其核威慑武器实施第一次打击的情形。而俄罗斯和中国也正是依靠自己庞大而多样的导弹武器，来威慑外国针对它们的军事行动，恐吓其他国家，凭借非对称反介入和区域拒止能力阻遏外国军队。

“萨德”被设计用来拦截飞近邻近目标的短、中程导弹或弹头。但它无法拦截瞄准美国的中国洲际弹道导弹，甚至无法拦截从中国向台湾、日本等不同方向发射的较短程导弹。

“萨德”系统先进的AN/TPY-2 远程雷达可以显著改善美国监视中国领土、尤其是收集中国核导弹力量情报的能力。

中国官方表示，“萨德”系统先进的AN/TPY-2 远程雷达可以显著改善美国监视中国领土、尤其是收集中国核导弹力量情报的能力。但这种能力不宜过分夸大。韩国的“萨德”系统将部署在半岛离中国最远的一端，而且设置在“末段/交战模式”，以监视朝鲜导弹，而不是深入中国进行监视。即使“萨德”可以监测中国的能力，其雷达所发现的东西也用处不大，因为美国已经通过空中、海上、太空、网络和和中国军政内部人员搜集了大量有关中国军队活动的数据。中国也在积极谋求同样的对付美国的能力。

不管技术上是怎样，俄罗斯和中国的代表都表示了对“萨德”给战略稳定、盟友关系和全球带来影响的总体担忧。他们警告说，朝鲜的回应会是加紧发展进攻性导弹，因为布署“萨德”让朝鲜觉得更不安全。他们呼吁美韩两国通过与中俄合作，解决朝鲜这类地区安全威胁，而不是采取部署“萨德”这种无视和可能危及中俄两国安全的行动。

俄罗斯和中国指责说，美国是利用来自朝鲜的威胁，为加强其在中俄周边的军事存在和军事力量找借口，并鼓动友邦和盟国加强自卫能力。它们反对“萨德”，反对美军采取其他措施提高效率，加强互通互联，巩固美国的军事同盟。它们也许希望通过阻止美国与盟国的导弹防御合作制造盟国之间的紧张，从而削弱美国全球防御保障的可信度。

中国人很可能恼羞成怒，因为他们向首尔示好的努力未能阻止韩国决定部署“萨德”。但中国政府为阻止韩国同意部署“萨德”而对首尔全场紧逼，效果适得其反。它给人的印象，是试图操控韩国的国家安全决策，利用“萨德”问题分化韩美，削弱韩美同盟。所幸，中国看来抵住了放宽联合国对朝制裁、弱化中韩经济社会关系的诱惑。而韩国其实愿与中国保持良好关系，希望与北京和衷共济解决共同面对的朝鲜问题。

Following months of assessment by a Joint Working Group, the U.S. Defense Department announced last week that the U.S. Forces Korea Command will station a Terminal High-Altitude Area Defense (THAAD) battery in the Republic of Korea (ROK) as “a defensive measure to ensure the security of South Korea and that of its people, and to protect alliance military forces from North Korea's weapons of mass destruction and ballistic missile threats.”

Image of the "THAAD" anti-missile defense rockets.（Source:CRI Online）

The decision followed years of delays during which Washington and Seoul strived but failed to curtail the nuclear and missile buildup of the Democratic People's Republic of Korea's (DPRK) through diplomacy and sanctions, including in partnership with China and Russia. Since the beginning of this year, North Korea has detonated its fourth nuclear explosive device, which Pyongyang claimed was a hydrogen bomb, and tested numerous missiles of varying length, including a Musudan (Hwasong-10) intermediate-range ballistic missile a few weeks ago. The Musudan can reach a height of 1,400km and has a range of 3,500km—a flight envelope beyond the ROK's Korea Air and Missile Defense (KAMD)'s limited capabilities of intercepting short- to medium-range ballistic missiles.

The Defense Department's announcement stressed that the new THAAD system “will be focused solely on North Korean nuclear and missile threats and would not be directed towards any third-party nations.” Nonetheless, the Russian and Chinese governments have attacked the decision on various grounds.

For example, Russian Deputy Foreign Minister Igor Morgulov denounced what he called a “buildup of the U.S. global anti-missile potential in [the] Asia-Pacific and an attempt to change the existing balance of power.” He claimed that the step will “inevitably lead to escalation in Northeast Asia and hinder settlement of the Korean Peninsula problem, including its denuclearization.”

The Chinese Foreign Ministry went even further and demanded that Washington and Seoul “halt” the planned THAAD deployment. Spokesperson Lu Kang called the measure “selfish” and claimed that the deployment would threaten peace and stability, escalate tensions on the Korean Peninsula, and “gravely damage the strategic balance in the region as well as the strategic security interests of countries in the region including China.” In addition, Lu threatened “necessary measures to safeguard [Chinese] interests if the United States and ROK don't stop the deployment.”

John Kirby, a State Department spokesperson, said that the United States has “listened to [Chinese] concerns and we have offered to provide informational briefings for them on the way the system works.” U.S. officials also made the same offer to Russia. However, such briefings have not proved fruitful since Russian and Chinese interlocutors distrust the message and the messenger. Regardless, their opposition to U.S. Ballistic Missile Defense (BMD) is driven mostly by geopolitical rather than technical considerations.

It is true that both Russian and Chinese military planners can postulate scenarios about how missile defenses could facilitate a U.S. first strike against their nuclear deterrents. Furthermore, Moscow and Beijing depend on their large and varied missile arsenal to deter foreign military actions against them, intimidate other countries, and keep foreign militaries away with asymmetric anti-access and area-denial capabilities.

THAAD is designed to intercept short- and medium-range missiles or their warheads when they are descending toward a nearby target. THAAD, however, is incapable of intercepting Chinese Intercontinental-Range Ballistic Missiles aimed at the United States or even shorter-range systems launched from China in a different direction, such as against Taiwan or Japan.

THAAD's sophisticated AN/TPY-2 X-Band radar could markedly improve the U.S. ability to monitor Chinese territory and, in particular, acquire intelligence about the capabilities of China's nuclear missiles.

Chinese officials claim that THAAD's sophisticated AN/TPY-2 X-Band radar could markedly improve the U.S. ability to monitor Chinese territory and, in particular, acquire intelligence about the capabilities of China's nuclear missiles. But its capabilities should not be exaggerated. THAAD in the ROK would be stationed at the farthest end of the peninsula away from China; likewise, it would be kept in “terminal/engagement mode” to monitor North Korean missiles rather than peer deep into China. Even if THAAD could monitor Chinese capabilities, the insights gained from the radar would hardly matter since the United States already collects enormous data about Chinese military activities through air, sea, space, and cyber-based sensors as well as human assets within the Chinese military and government. China is actively seeking the same capacity against the United States.

Regardless of the technological issues, Russian and Chinese representatives have expressed general concerns about how THAAD could affect strategic stability, alliance relations, and global influence. They warn that Pyongyang will respond by accelerating its offensive missile buildup because the deployment will make North Korea feel more insecure. They call on Washington and Seoul to work in partnership with Beijing and Moscow to solve regional security threats like North Korea rather than taking actions, such as THAAD deployment, that ignore and allegedly harm Chinese and Russian security.

The Russians and the Chinese accuse Washington of exploiting the threat from North Korea to justify expanding U.S. military presence and capabilities near their territories and encouraging U.S. friends and allies to increase their own defenses. They also oppose THAAD and other U.S. military measures that strengthen U.S. alliances by making them more effective and interlinked. They might hope that by blocking U.S. allied missile defense cooperation they can incite tension in the alliance and weaken the credibility of U.S. global defense guarantees.

The Chinese might also be irritated that their efforts to court favor in Seoul failed to prevent Seoul's deployment decision. But the Chinese government's full-court press in Seoul to deter South Korea from agreeing to the deployment backfired. China gave the impression of trying to control South Korea's national-security decision-making and weaken the ROK-U.S. alliance by leveraging the THAAD issue to divide them. Fortunately, China looks to be resisting the temptation to relax enforcement of UN sanctions on North Korea or to curtail economic and social ties with South Koreans, who want good ties with China and to partner with Beijing in order to solve their common DPRK problem.