From where did the concept of missile defence emanate? And why has missile defence been and continues to be a controversial issue and not, as so many other inventions in the continuous chain of measures and countermeasures, just another self-evident instrument in a defence posture? The purpose of this chapter is to look more closely at these questions and search for the specific aspects of missile defence not so much as a technological system but as a strategic option. Missile defence is here discussed in the broader context of active air defence from the world wars to the present. The evolution of strategies of missile defence is a predominately, but not exclusive, US phenomenon. The Soviet and Russian experience is dealt with in another chapter. My point of departure is a general concept or model for response to

new strategic offensive systems. The interaction of measures and countermeasures over the various fields of warfare basically reflects similar strategic trade-offs and choices. Which are the defensive or responsive options available? And why do states and military organizations choose among them the way they do? In the great battleship arms race preceding the First World War, the

obvious choice for the major contenders was to construct bigger, more heavily armoured and armed and faster battleships at a rate matching or outbuilding potential opponents. For the secondary naval powers this was not within reach and other options had to be considered. One was to adjust overall naval ambitions and concentrate on coastal defence. The purpose of

coastal defence battleships was not to match the Dreadnought-type battleships but to force a major naval power to commit the most powerful ships in an engagement with a secondary navy. But as new technologies emerged, new strategic choices became available.

Instead of countering gunships with gunships, La Jeune E´cole in the late nineteenth century emphasized technological change, countermeasures and alternative strategies. The giants should not be met with giants but with new strategies based on smaller ships and torpedoes, successfully employed in the First World War by the Italians against the Austro-Hungarian navy. And in the Second World War another technological system, ground-and carrierbased aircraft, emerged as both the ultimate countermeasure and a superior replacement for the battleships. Nuclear weapons forced all the major powers to consider possible

counter-strategies for coping with the specific kind of threat posed by weapons of mass destruction. These emerging counter-strategies can be described as a number of choices along a ladder or a stair, where the highest steps represent the forward and preventive strategies and the lowest the most passive and reactive strategies (see Figure 1.1). Abolition is an ultimate strategy; a non-existing (or preferably non-

invented) threat does not require any further counter-strategies. Nonproliferation is a choice in a situation where not the weapons themselves but rather their diffusion is perceived as the main problem, as was the case after deterrence was established between the superpowers. Without deterrence there is a range of operational options for preventing, blunting, fending off or limiting a strike with WMD. This can be done by attacking production facilities, bases and offensive weapons systems, or through defensive measures through successive layers. Finally, passive measures can be employed with the aim of damage limitation. And of course, in the best of worlds the

population can be reassured that no such thing as a devastating attack with WMD will ever take place. These reactive/pre-emptive choices have three main dimensions. The first

is about technology and resources. Civil defence became a key strategy in early Cold War planning since the air (and later missile) defence problem could not be solved. And civil defence was largely abandoned as the destructive power of the nuclear arsenals surpassed any protective countermeasure. The second dimension is about warfare and force postures. The shift from massive retaliation to flexible response in the 1960s was an attempt to redefine the role of nuclear weapons in warfare and thus to reduce the need for reactive defensive measures. The third dimension is about international politics. The growing number of threshold states in the 1960s compelled the international community, with some important exemptions, to support the establishment of the Non-Proliferation Treaty, thus transforming proliferation issues from bilateral relations to a multilateral international regime. This dynamic of technology, warfare and international politics remains at the core of the issue of strategies to counter WMD threats.1