destroy Soviet missiles before they reached the United States. SDI was criticized by both the Soviets and many of America's allies (including Prime Minister of the United Kingdom Margaret Thatcher) because, were it ever operational and effective, it would have undermined the "assured destruction" required for MAD. If the United States had a guarantee against Soviet nuclear attacks, its critics argued, it would have first-strike capability, which would have been a politically and militarily destabilizing position. Critics further argued that it could trigger a new arms race, this time to develop countermeasures for SDI. Despite its promise of nuclear safety, SDI was described by many of its critics (including Soviet nuclear physicist and later peace activist Andrei Sakharov) as being even more dangerous than MAD because of these political implications. Supporters also argued that SDI could trigger a new arms race, forcing the USSR to spend an increasing proportion of GDP on defense—something which has been claimed to have been an indirect cause of the eventual collapse of the Soviet Union. Gorbachev himself in 1983 announced that “the continuation of the S.D.I. program will sweep the world into a new stage of the arms race and would destabilize the strategic situation.” Proponents of ballistic missile defense (BMD) argue that MAD is exceptionally dangerous in that it essentially offers a single course of action in the event of a nuclear attack: full retaliatory response. The fact that nuclear proliferation has led to an increase in the number of nations in the "nuclear club", including nations of questionable stability (e.g. North Korea), and that a nuclear nation might be hijacked by a despot or other person or persons who might use nuclear weapons without a sane regard for the consequences, presents a strong case for proponents of BMD who seek a policy which both protect against attack, but also does not require an escalation into what might become global nuclear war. Russia continues to have a strong public distaste for Western BMD initiatives, presumably because proprietary operative BMD systems could exceed their technical and financial resources and therefore degrade their larger military standing and sense of security in a post-MAD environment. Russian refusal to accept invitations to participate in NATO BMD may be indicative of the lack of an alternative to MAD in current Russian war-fighting strategy due to the dilapidation of conventional forces after the breakup of the Soviet Union. Proud