US missile defence
Strategy, technology and politics

Re-produced with the kind courtesy of STRATEGIC COMMENTS of the International Institute for Strategic Studies

OVER A RELATIVELY SHORT PERIOD, theatre missile defence (TMD), and, still more, national missile defence (NMD) have become two of the most keenly debated issues on the US security agenda. Technological developments have meant that plans for TMD and NMD, previously separate, have become increasingly intertwined.

However, programmes in this field are also being driven by vested interests in the armed services and the military-industrial complex. Politicians in Congress have taken rigid positions, and all sides are making claims and counter-claims which are often out of proportion to current technological and financial realities. Issues have become politicised long before deployment decisions need to be made. This may unnecessarily complicate US strategic calculations and relations with other powers.

Origins of missile defence

TMD was initially conceived purely in terms of protection for US forces against conventionally armed enemy missile strikes. Support for investment in this area was galvanised by Iraqi Scud missile attacks on American troops stationed in Saudi Arabia during the 1991 Gulf War. These attacks killed 28 US military personnel and raised major questions about the effectiveness of existing Patriot missile defence batteries. The immediate result was the passage by Congress of the 1991 Missile Defence Act, stipulating significantly greater funding for research and development.

In the course of the 1990s, the diffusion of ballistic-missile technology and the proliferation of chemical, biological and nuclear weapon capabilities meant that the perceived risk from 'rogue state' missiles grew enormously. Regimes like North Korea were seen to be developing a ballistic missile capability that could strike America's regional allies and even, in future, the territory of the US itself. As a result of these challenges, the need for TMD to defend US troops in the field, backed by a solid consensus among US politicians and policy makers, became mixed up with demands for a national-missile-defence system.

NMD, however, is much more controversial, for reasons of cost and diplomatic impact and because the technology is mainly unproven. Many experts simply do not think that an effective NMD shield can be developed in the foreseeable future, at least not without a massive diversion of resources away from more pressing security requirements.

Developments in East Asia, particularly in North Korea, have given an important boost to demand for TMD and NMD. In May 1993, Pyongyang tested its Nodong missile - its estimated range of 1,000 kilometres reached more than half of Japan. Since the test, the Nodong has been deployed in North Korea, and its technology has been exported to Pakistan.

China made a series of unarmed launches of its DF-15 missile - better known by its export designation, the M-9 - during its 1995-96 military exercises opposite Taiwan. With a range of 600km, the M-9 can hit targets throughout Taiwan. At the time of the exercises, US officials estimated that the Chinese had no more than 50 missiles deployed in coastal areas within range of Taipei. However, a leaked US intelligence report in January 1999 indicated that the total inventory opposite the Republic - consisting of M-9s and shorter-range M-11s- had grown to 150-200 missiles, and would rise to more than 600 by 2005 if recent trends persist. These figures have, however, been contested by some US analysts, who believe that China's programme is much smaller.

US support for missile defence was greatly increased following the unexpected first test by North Korea, on 31 August 1998, of the Taepodong 1 missile, a three-stage rocket with an estimated range of more than 2,000km. The object of the exercise - to place a satellite in orbit - was not achieved, but this was a minor matter compared with the successful use of multistage technology.

The missile flew over Japanese territory, shifting the balance of opinion in Tokyo decisively in favour of providing financial support for TMD through a joint research programme with the US. In America - where few in the intelligence community had expected North Korea to develop a multi-stage missile by such an early date-the test appeared to vindicate the judgements made in 1998 by a high level bipartisan panel, chaired by former Secretary of Defence Donald Rumsfeld. The panel predicted that certain adversaries could build intercontinental missiles capable of reaching targets in the US within five years of deciding to do so. This view was reinforced by Pakistan's test of its Ghauri missile in April 1998, and by Iran's test of the Shihab 3 in July. The latter came as a particular shock to US analysts, who had not thought that even Russian technology would have enabled Iran to make such progress in so short a period of time.

Shift in US policy

These developments added to longstanding pressure from Republicans in Congress for both TMD and NMD development to be speeded up, although most systems were, at best, in the early stages of testing and evaluation. President Bill Clinton's administration repeatedly sought to propitiate its critics, but it was far more cautious than Congress over NMD, and a lot more concerned about the implications of missile-defence programmes for maintaining the 1972 Anti-Ballistic Missile (ABM) Treaty with Russia.

On 20 January 1999, however, the administration shifted course. Defence Secretary William Cohen announced that the US was adding $6.6 billion to the Future Years Defence Plan for NMD. Administration spokesmen also referred much more explicitly to the need to renegotiate the ABM Treaty - provoking a furious response in Moscow.

Defence in layers

There are three distinct sets of missile-defence capabilities at varying levels of technological maturity:

  • 'lower-tier' systems designed for defence of specific locations or tar- gets - more suitable for TMD;
  • 'upper-tier' systems intended to intercept warheads in flight, and capable of covering a much wider area - more appropriate for NMD; and,
  • a host of sensors, radars and battle- management capabilities intended to detect missile launches, thereby pro- viding timely warning of an impend- ing attack.

In an optimal scenario, a spectrum of these capabilities would be arrayed in layered fashion to ensure the thickest possible defensive shield.

There is also a fourth level of capability, still at a conceptual stage but suitable in principle for both TMD and NMD. This focuses on intercepting and destroying missiles during their initial boost phase-that is, before warheads or decoys break away and head for their targets. Most attention has been paid to the potential for airborne or space-based lasers, or 'kill vehicles' launched from a manned or unmanned plane.

Many of these systems entail an array of complex, largely unproven technologies. Even if they prove fully reliable - a big assumption -there will be other daunting issues to confront, such as cost and disputes over which US service should develop and control the systems. There will also be very difficult questions of interpretability with various US allies. In addition, these projects currently pay minimal attention to the likely prospect of enemy countermeasures, including: attempts to paralyse electronic systems; use of cruise missiles to circumvent antiballistic-missile shields; and attempts simply to overwhelm defences with large numbers of missiles.

Even more fundamentally, much of the current debate fails sufficiently to address the previous US strategic doctrine that a state such as North Korea would automatically be deterred from firing its missile at the US by the prospect of massive retaliation from America's own nuclear inventory. This arsenal, after all, deterred a much larger Soviet threat during the Cold War, and its continued presence has led some analysts to question whether the immense costs of NMD development are justified.

By contrast, 'lower-tier' systems, primarily suited to TMD, enjoy general support. Enhancements of existing capabilities have made them cheaper, and the technology is better proved. There is also less rivalry between the armed services, since the principal platforms under development fulfil complementary defence needs. These systems are the Patriot Advanced Capability (PAC)-3 designed to protect land-based US and allied forces, and the Navy Area Defence (NAD), to be deployed on Aegis-class cruisers to defend coastal targets. The successful test of a PAC-3 interceptor in mid-March 1999 boosted hopes of initial deployment by 2001. However, PAC-3 is geared to intercepting slower-moving incoming missiles at very close range, over a relatively small area, and cannot provide a basis for a NMD shield.

Upper-tier options

Among the new 'upper-tier' systems under development, the greatest efforts have been devoted to Theatre High Altitude Area Defence (THAAD). The concepts and technologies involved in this army programme are much more advanced than those of PAC-3. THAAD is designed to intercept targets at a much greater range - including outside the atmosphere - and over a much larger area. According to advocates, the system could be integrated with a full spectrum of space-based sensors, enabling it to intercept incoming warheads at ranges of up to several hundred kilometres. To date, however, THAAD's reach has consistently exceeded its grasp. Despite prodigious budgetary allocations throughout the 1990s, THAAD tests failed six times in a row. The latest failure, in late March 1999, led many observers to question the programme's viability.

This provides the ship-based Navy Theatre-Wide (NTW) system with a major opportunity. NTW supporters argue that the system is more flexible and more capable than THAAD, and obviates the need for possibly controversial deployments on allied territory. It has been designed with a more rapid interceptor, and will purportedly be able to cover a wider area than THAAD.

Cohen's announcement on 20 January 1999 increased funding for the NTW programme. The intention is to accelerate testing of both THAAD and NTW over the next few years, allowing for early evaluation and a decision on which will be the lead 'upper-tier' programme. The goal is initial deployment of that system in 2007.

The prospect of advanced TMD deployment seems almost certain to trigger major expectations and concerns in other countries. These include Japan, which must balance compelling security needs against its fear of worsened relations with China. For Taiwan, TMD presents an opportunity substantially to augment defence collaboration with the US while reducing China's strategic advantage. This is, of course, what worries Beijing. Chinese analysts are sceptical about America's ability to develop an NMD capability, but they are very concerned that a greatly enhanced US TMD system in East Asia, including Taiwan, would seriously tip the existing strategic balance against China. Beijing has made it clear that moves in this direction will worsen Sino-US relations. But it is precisely because an East Asian TMD system may have a realistic chance of limiting Chinese power - which many Americans see as increasingly threatening - that further US moves in this direction seem inevitable.

Capability and cost of main theatre missile defences

System name Type of warhead Approx. radius of defended area Units  Date of initial deployment Acquisition cost
Lower-tier (Point) defences
Patriot PAC-2 (army) Blast fragment 10-15km 2,247 missiles modified  1991 US$0.3bn
Patriot PAC-3 (army)  Hit-to-kill 40-50km 1,200 missiles, 54 fire units 1999 US$6.2bn
Navy Area Defence Blast fragment 50-100km 1,500 missiles 2000 US$6.2bn
(Navy lower tier)
Upper-tier (area) defences
THAAD (army) Hit-to-kill A few hundred km 1,233 missiles, 2006` US$ 12.8bn
77 launchers, 11 radars
Navy Theatre-Wide Defence Hit-to-kill A few hundred km 650 missiles on 22 Aegis cruisers -- US$ 5.0bn
(Navy upper tier)