For several decades during the cold war, the US Berlin Brigade (and its British and French counterparts) defended West Berlin. What could those hugely outnumbered American soldiers have done had the Red Army attacked? As strategist Thomas Schelling bluntly put it, they could die – heroically perhaps – but in any case American military power would seek to avenge them. That tripwire deterred the Soviets and kept West Berlin free.

冷战的数十年间，美军柏林旅(Berlin Brigade)（同英法士兵一道）保卫着西柏林。如果苏联红军发起进攻，寡不敌众的美国士兵能做些什么呢？如同战略家托马斯•谢林(Thomas Schelling)不客气地指出的一般，美国士兵会被杀死（也许是英勇就义），但美国军队无论如何都会为他们报仇。这个绊索让苏联不敢轻举妄动，也让西柏林保持着自由。

Given Moscow’s aggression in Ukraine, companies of airborne soldiers have been deployed to Estonia, Latvia, Lithuania and Poland to assure those countries and serve as tripwires. But the soldiers are all Americans. Where are the Europeans? Their absence could lead to miscalculation in the Kremlin and questions in US Congress.

由于俄罗斯入侵乌克兰，空降兵连被派遣至爱沙尼亚、拉脱维亚、立陶宛和波兰，为的是让这四国放心，同时起到“绊索”作用。但所有这些士兵都是美国人。欧洲士兵在哪里？欧洲士兵的缺席会使克里姆林宫产生误判，也会在美国国会引发质疑。

In the past three months, Moscow has seized Crimea by force and roiled the waters in eastern Ukraine. President Vladimir Putin asserts a right to protect ethnic Russians and Russian speakers wherever they live and regardless of their nationality. That understandably worries Nato members Estonia and Latvia, countries in which 1 in 4 citizens is an ethnic Russian.

过去三个月里，俄罗斯通过武力夺取了克里米亚(Crimea)，使得乌克兰东部地区暗潮四起。俄罗斯总统弗拉基米尔•普京(Vladimir Putin)坚称，俄罗斯有权保护俄罗斯族与讲俄语的人，无论这些人在哪里生活、国籍是什么。北约(NATO)成员国爱沙尼亚和拉脱维亚有四分之一的公民都属俄罗斯族，可想而知，此举令这两个国家感到担忧。

As the crisis has deepened, Nato has made measured military deployments to allies on its eastern flank. Initially, in March, fighter aircraft and naval vessels were sent, mostly American. Poland, Britain and Denmark have also deployed fighter planes to the Baltic states.

随着危机的加深，北约已慎重地向其东部盟国部署了军事力量。一开始是在3月份部署了战斗机和军舰，其中大多是美国军力。波兰、英国及丹麦也向波罗的海(Baltic)国家部署了战斗机。

European ground troops have taken part in exercises in the region, but they are not staying. The US army in April deployed companies of 150 soldiers each to Poland, Lithuania, Latvia and Estonia; the Pentagon said they would maintain a “persistent” presence for perhaps as long as a year, providing the states in which they are stationed with tripwires. Yet the solely American nature of the persistent ground force deployments is not healthy for Nato.

欧洲国家的地面部队参与了该地区的军事演习，但没有驻扎下来。4月，美国向波兰、立陶宛、拉脱维亚和爱沙尼亚各部署了由150名士兵组成的连队。五角大楼(Pentagon)称，美军或许会“持续”驻扎长达一年的时间，为这些国家提供军事保障，起到“绊索”作用。但长期部署的地面武装部队全由美国人组成，这于北约没有益处。

The Kremlin may see an alliance divided. It can hardly have escaped Moscow’s notice that, in the past two months, the EU has balked at the strongest sanctions Washington has sought to apply. Will the Russians now conclude that the effort to assure eastern allies is more American than Nato? If so, Moscow may attempt to drive a wedge between the US and its Nato allies.

克里姆林宫可能因此把北约看作一个意见分歧的同盟。过去两个月里，美国寻求对俄实施最严厉制裁，欧盟却踌躇不决，这难以逃过莫斯科的注意。俄罗斯是否会得出结论，认为对北约东部盟国的军事保障更多地来自美国而非北约？如果是的话，莫斯科可能会试图离间美国与其北约盟国。

Mr Putin seems intent on challenging the alliance. The dearth of European boots on the ground might lead the Kremlin to a dangerous conclusion: that important allies might not be prepared to carry out their commitment under Nato’s Article 5 to defend the Baltic states. The consequences could be disastrous.

普京似乎有意向北约发出挑战。地面武装力量中缺乏欧洲军力可能使克里姆林宫得出一个危险的结论：北约重要盟国也许不准备履行北约宪章第五条关于保卫波罗的海国家的承诺。其后果将是灾难性的。

US defence spending takes 4 per cent of gross domestic product, while most Nato allies fall short of the alliance’s agreed target of 2 per cent. US military spending is 2.5 times greater than that of all its European Nato allies combined. The American defence budget has come under close scrutiny in Congress, at a time when some voices are questioning the need for so much engagement abroad.

美国国防开支占其国内生产总值的4%，而大部分北约盟国的国防开支都达不到北约所约定的2%指标。美国军费支出是其北约欧洲盟国军费支出总和的2.5倍。在一些声音质疑美国是否有必要参与如此之多的海外军事行动之际，美国国防预算受到了国会的严格审查。

If Congress perceives US allies as unready to respond seriously to the collective defence requirements of their neighbours, it may question whether America should pay so much attention to Article 5. That would seriously weaken Nato.

如果美国国会认定美国盟国不准备对其邻国的集体防御请求做出认真回应，国会可能会质疑美国是否应当如此重视北约宪章第五条。这会严重地削弱北约。

The lack of a sustained European ground presence has another unintended impact. The fewer conventional forces are committed to their defence, the louder will be the insistence from Baltic and central European allies that US nuclear arms remain in Europe. Allies such as Germany, the Netherlands and Belgium have expressed a desire to see the US nuclear presence reduced. Without robust conventional assurance, however, nuclear arms are likely to stay.

欧洲地面军力不能长久部署还有一个意想不到的后果。用于防御的常规部队力量越少，波罗的海及中欧盟国坚持美国继续在欧洲部署核武器的呼声就越强。德国、荷兰及比利时等盟国已表达了希望美国减少在欧洲部署的核武器的愿望。但如若缺少强大的常规军力保障，核武器很可能会继续部署在欧洲。

Nato needs to do more on its eastern flank. European armies should match the US commitment with four companies of their own.

北约需加强在东部地区的部署。北约欧洲盟国也应派出自己的四支连队，与美国军力相协调。

Paired US and European companies would form joint tripwires. The deployments would cost relatively little. Light infantry numbering 300 troops in each of the four countries would pose no offensive military threat to Russia. Such paired deployments would, however, do much to bolster assurance for Nato’s eastern members and underscore the red line that protects all alliance members.

美国连队与欧洲连队的部署组合将形成联合绊索。这种部署的成本也相对较低。在4个国家每国部署300名轻步兵不会对俄罗斯造成军事进攻威胁。但这种部署组合能大大提高北约东部盟国的军事保障，使保卫所有盟国这条红线更加凸显。