The editorial "BMD: What's in a word?" (6/27), presented a misleading argument by claiming that by maintaining a modern and robust nuclear arsenal we retain our security. This argument neglects the dramatic changes that have occurred through the proliferation of nuclear warhead and missile technology in the past thirty years.

We were both heavily involved in the fields of nuclear offense and defense when President Reagan introduced the SDI program in March 1983. Orman had been the chief engineer responsible for the introduction of the Chevaline system as the British nuclear deterrent, and Fox was placed in charge of the Homing Overlay experiment that demonstrated the possibility of achieving a direct hit to destroy an attacking missile without use of a nuclear warhead.

Later we worked in tandem as the director general of the UK SDI Participation Office and as DD of the US SDI Organization. What was clear at the time was that apart from President Reagan and Prime Minister Thatcher, few other political leaders grasped the significance of the importance of the SDI program.

Deterrence, by the threat of overwhelming retaliation worked effectively throughout the Cold War, but Reagan and Thatcher recognized that the possession of a reliable nuclear arsenal combined with an effective defense system would provide significantly enhanced security. The significance of the words "reliable" nuclear arsenal" and "effective" missile defense should not be overlooked. A limited capable defense was never in the minds of the two leaders; it would merely be a starting position from which improvements had to be made.

After the introduction of the SDI program the Reagan administration recognized it had to counter the allied perception that a defense of the US alone might adversely affect the extended nuclear deterrence under which so many other nations had felt secure for decades. As a result the US modified its initial requirement for missile defense, later referred to as anti-ballistic missile defense [ABM], to intercept all attacks on a global scale, thus bringing allies under the protection umbrella.

The modified requirement has remained as a capability to defend globally against missiles of all ranges in all phases of their flight. Such an objective was always recognized as being difficult to accomplish, although at the time it was hoped that speed-of-flight weapons, such as lasers and particle beams, would enable rapid and effective interception of attacking missiles. These assets have not yet materialized, and we are still dependent on limited numbers of ground-based missiles capable of intercepting small raids during their midcourse and terminal phases of attack.

During the Clinton administration, the Defense Department was directed to concentrate on the terminal phase of tactical defense that could be accomplished with the equipment then under development, and sadly there has been little enhancement of the US strategic defense against the steadily improved modern missiles becoming available to hostile nations. The editorial seems not to recognize that after 33 years of active development, the systems currently deployed are still well short of meeting the longstanding defense requirements.

What has changed in the intervening period has been the acquisition of nuclear offensive systems by powers that are far less likely to be intimidated by the threat of overwhelming retaliation. Even more concerning is that the observed proliferation increases the risk that some of these countries might be tempted to provide systems to terrorist groups that would not be deterred by threats of retaliation. The world has become far more unstable since BMD was introduced to enhance what was then a reasonably effective deterrent policy, the need for a far more efficient BMD is greater now, merely to return to the level of security we had previously.

The editorial concluded "Congress should let the science play out on missile defense before rushing for an expansion." An odd conclusion when Congress and the DOD have been far too slow to recognize the growing danger, one that has been pointed out repetitively for the past 25 years. Without some form of space-based defense we cannot achieve the BMD requirements that have been in existence for decades.

It was never the intention of those who understood the importance of a defense increasing the effectiveness of deterrence to settle for a limited capability, one that even now might not be fully effective against what we once called third-world nations. The world has changed but sadly the thinking of too many of our leaders remains locked into a past that is no longer relevant. Yes, a space-based defense might be costly, but without it we are only fooling ourselves that we have a defense.

Eugene Fox is vice president and Stanley Orman chief executive of Orman Associates, a defense and international consultancy, Rockville, Maryland.