SOVIET preparations at the Reykjavik summit focused on carrots to tease limitations on the Strategic Defense Initiative (SDI) out of President Ronald Reagan, while American tactics undoubtedly included layers of protection to limit concessions and to prevent damage to the program. But the two leaders were looking exclusively at the two ``standard'' versions of SDI: ``SDI I,'' the total shield that President Reagan proposed, and ``SDI II,'' which has the much closer goal of a quick deployment to protect United States missiles and bust the Anti-Ballistic Missile Treaty once and for all. Neither SDI I nor SDI II is likely to be effective soon, except at destroying the ABM Treaty. But two new parallel programs can be envisioned -- SDI III and SDI IV -- which might hold out real promise for increasing the security of both countries in less than five years.
Construction of SDI I is an option only in the next century, if ever. Even if it were built in the near future, SDI II would serve the American people poorly. Soviet planners might perceive that a near-term missile defense, being leaky, could be overwhelmed by modest increases in offensive striking power. The Soviets might then choose to offset a US defense by increasing the number of warheads aimed at US missiles.
If the Soviets overestimate the performance of our defense, while prudently underestimating the capabilities of their own missiles, more warheads might hit US targets than would if this country remained defenseless. Furthermore, the Soviet Union will never permit a unilateral American action to disarm its strategic forces.