On 23 March 1983 Ronald Reagan publicly announced development of the Strategic Defense Initiative . The Soviet government felt that the purpose of SDI technology was to render the US invulnerable to Soviet attack , thereby allowing the US to launch missiles against the USSR without fear of retaliation . This concern about a surprise attack prompted the sudden expansion of the RYAN program . The level of concern reached its peak after the Soviets shot down KAL 007 near Moneron Island on 1 September 1983 , and during the North Atlantic Treaty Organisation exercise Able Archer 83 . The Soviet Union believed that a United States first strike on the Soviet Union was imminent
KAL 007
Korean Air Lines Flight 007
RYAN