> In 2014, a declassified CIA paper stated that "In response to SDI, Moscow threatened a variety of military countermeasures in lieu of developing a parallel missile defense system".

The Soviets had very capable scientists who could figure out - like Bethe in the US - that SDI was not feasible, and the easy work-around is to launch more missiles, not build their own SDI.

Or for something more scholarly, from "Did Star Wars Help End the Cold War? Soviet Response to the SDI Program" at https://scienceandglobalsecurity.org/archive/sgs25podvig.pdf Science & Global Security, 2017, 25.1: 3-27.

> The evidence on the Soviet response to SDI that emerges from the internal documents largely corroborates the view that the Soviet Union eventually realized that this program did not present a danger to its security because it could be relatively easily countered with simple and effective countermeasures.

Since gadders' comment is flagged, I don't know the fuller context.

That is, as far as I can tell, it agrees with me ("responses to SDI were not a major factor in either the collapse of the Soviet Union, nor in the end of the Cold War"), including by citing the same source I gave, the paper by Pavel Podvig.