經過一個聯合工作小組數月的評估，美國國防部近日宣布，駐韓美軍司令部將在韓國部署末段高空區域防禦系統（“薩德”），作為“保障韓國及韓國人民安全的防禦措施，同時防止盟軍部隊受朝鮮大規模殺傷性武器和彈道導彈的威脅。”

“薩德”反導系統資料圖（選自：國際在線）

這一決定已經遲到了好幾年。其間，華盛頓和首爾想通過外交和制裁，包括與中俄合作，來阻止朝鮮發展核武器和導彈，但這一努力以失敗告終。今年年初以來，朝鮮試爆了被它稱為氫彈的第四個核裝置，並試射了多枚各種射程的導彈，包括幾周前的“舞水端（化城-10）”中程彈道導彈。“舞水端”射高可達1400公里，射程3500公里，飛行包線超過了韓國導彈防禦系統（KAMD）短、中程彈道導彈的有限攔截能力。

美國國防部的聲明強調，新“薩德”系統“只針對朝鮮核武器和導彈威脅，不會針對任何第三國”。然而，俄羅斯和中國政府以種種理由對這一決定展開抨擊。

例如，俄羅斯副外長伊戈爾·莫古洛夫指責“美國在亞太建立全球反導能力，試圖改變現有力量平衡”。他聲稱，此舉將“不可避免地導致東北亞緊張局勢升級，妨礙去核化等朝鮮半島問題的解決。”

中國外交部更進一步要求美國和韓國“中止”部署“薩德”。發言人陸慷稱此舉完全是出於“一己私利”，認為部署“薩德”將威脅和平與穩定，使朝鮮半島緊張局勢升級，“嚴重破壞地區戰略平衡，損害包括中國在內的域內國家的戰略安全利益”。

美國國務院發言人約翰·柯比表示，美國已經“聆聽（中國人的）關切，並向他們提供了這一系統工作方式的情況通報”。美國官方也向俄羅斯提供了同樣的通報。然而，通報沒有收到什麼效果，因為俄中兩國參與對話的人員對前來通報情況的人及相關信息並不信任。不管怎樣，他們反對美國彈道導彈防禦系統（BMD）主要是着眼於地緣政治，而非技術考量。

的確，俄中兩國軍事策略家們可以假設導彈防制系統如何幫助美國對其核威懾武器實施第一次打擊的情形。而俄羅斯和中國也正是依靠自己龐大而多樣的導彈武器，來威懾外國針對它們的軍事行動，恐嚇其他國家，憑藉非對稱反介入和區域拒止能力阻遏外國軍隊。

“薩德”被設計用來攔截飛近鄰近目標的短、中程導彈或彈頭。但它無法攔截瞄準美國的中國洲際彈道導彈，甚至無法攔截從中國向台灣、日本等不同方向發射的較短程導彈。

“薩德”系統先進的AN/TPY-2 遠程雷達可以顯著改善美國監視中國領土、尤其是收集中國核導彈力量情報的能力。

中國官方表示，“薩德”系統先進的AN/TPY-2 遠程雷達可以顯著改善美國監視中國領土、尤其是收集中國核導彈力量情報的能力。但這種能力不宜過分誇大。韓國的“薩德”系統將部署在半島離中國最遠的一端，而且設置在“末段/交戰模式”，以監視朝鮮導彈，而不是深入中國進行監視。即使“薩德”可以監測中國的能力，其雷達所發現的東西也用處不大，因為美國已經通過空中、海上、太空、網絡和和中國軍政內部人員搜集了大量有關中國軍隊活動的數據。中國也在積極謀求同樣的對付美國的能力。

不管技術上是怎樣，俄羅斯和中國的代表都表示了對“薩德”給戰略穩定、盟友關係和全球帶來影響的總體擔憂。他們警告說，朝鮮的回應會是加緊發展進攻性導彈，因為布署“薩德”讓朝鮮覺得更不安全。他們呼籲美韓兩國通過與中俄合作，解決朝鮮這類地區安全威脅，而不是採取部署“薩德”這種無視和可能危及中俄兩國安全的行動。

俄羅斯和中國指責說，美國是利用來自朝鮮的威脅，為加強其在中俄周邊的軍事存在和軍事力量找借口，並鼓動友邦和盟國加強自衛能力。它們反對“薩德”，反對美軍採取其他措施提高效率，加強互通互聯，鞏固美國的軍事同盟。它們也許希望通過阻止美國與盟國的導彈防禦合作製造盟國之間的緊張，從而削弱美國全球防禦保障的可信度。

中國人很可能惱羞成怒，因為他們向首爾示好的努力未能阻止韓國決定部署“薩德”。但中國政府為阻止韓國同意部署“薩德”而對首爾全場緊逼，效果適得其反。它給人的印象，是試圖操控韓國的國家安全決策，利用“薩德”問題分化韓美，削弱韓美同盟。所幸，中國看來抵住了放寬聯合國對朝制裁、弱化中韓經濟社會關係的誘惑。而韓國其實願與中國保持良好關係，希望與北京和衷共濟解決共同面對的朝鮮問題。

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.