According to this 1998 interview with Zbigniew Brzezinski, the CIA's intervention in Afghanistan preceded the 1979 Soviet invasion. This decision of the Carter Administration in 1979 to intervene and destabilise Afghanistan is the root cause of Afghanistan's destruction as a nation.
The CIA's Intervention in Afghanistan
Interview with Zbigniew Brzezinski,
President Jimmy Carter's National Security Adviser
Le Nouvel Observateur, Paris, 15-21 January 1998
Posted at globalresearch.ca 15 October 2001
Question: The former director of the CIA, Robert Gates, stated in his memoirs ["From the Shadows"], that American intelligence services began to aid the Mujahadeen in Afghanistan 6 months before the Soviet intervention. In this period you were the national security adviser to President Carter. You therefore played a role in this affair. Is that correct?
Brzezinski: Yes. According to the official version of history, CIA aid to the Mujahadeen began during 1980, that is to say, after the Soviet army invaded Afghanistan, 24 Dec 1979. But the reality, secretly guarded until now, is completely otherwise Indeed, it was July 3, 1979 that President Carter signed the first directive for secret aid to the opponents of the pro-Soviet regime in Kabul. And that very day, I wrote a note to the president in which I explained to him that in my opinion this aid was going to induce a Soviet military intervention.