Ronald Reagan gave the following 30-minute talk on March 23rd, 1983, i.e. 30 years ago:
Most of the talk is about the motivation and the situation. The very SDI comments begin at 25:00 or so.
The visionary SDI (Strategic Defense Initiative) speech was arguably the most consequential presidential speech in the modern U.S. history. I am somewhat impressed by the depth of the technical arguments that Reagan offered.
In July 1979, Reagan would visit some defense folks in Colorado and they showed him that the Mutually Assured Destruction doctrine was the only possible conclusion. Ronald Reagan couldn't accept such an attitude and the speech above symbolized what he wanted to do to protect the civilians against the Soviet-led attacks from outer space and change the doctrine.
I was 10 years old, I spoke no English, and today was actually the first time I listened to the speech above. But I remember that during a gym class, when I was a 3rd grader or a 4th grader, at the 21st Elementary School in Pilsen with an extended education of languages (Russian, in my case then), we suddenly had to listen to a bizarre scary speech in the school radio sometimes in 1983 or 1984 or so.
We were told that the international situation got worsened a lot and a war could be imminent. Of course, we were told about the imperialist warmongers all the time but this was the only time when I heard an announcement fully dedicated to a possibly looming war.
I have never reconstructed the date of that bizarre announcement or the reason behind it. Now, it seems plausible that Reagan's speech was what sparked the school radio announcement. Some commies at our school could have gotten anxious that the American imperialists could get really strong now and it's necessary to upgrade the war preparations and war rhetoric (although we've never heard anything that would be so pro-war as the North Korean propaganda we observe these days: the official propaganda would always paint us as the "camp of peace" while the capitalist world were the "warmongers").
At any rate, this was the impact of Reagan's speech on the Soviet politicians. Arms races escalated and they effectively led to the surrender of the Soviet Union. It has overspent the money for arms races. This caused some problems in the economy and that helped Gorbachev to be elected and ultimately terminate the totalitarian Cold War era in the Soviet Union – and, indirectly, in the whole Soviet bloc.
Many people – especially left-wingers – have been trying to humiliate the SDI. In 1987, the American Physical Society joined these critics and questioned whether the SDI is allowed by the laws of physics. But it's clear that "something like that" may be immensely useful and nowadays, similar technologies belong to the responsible defense strategists' standard toolkit. The critics usually employ excessively high standards when they evaluate the SDI. They say that because the technology can't be perfectly reliable under all circumstances, it's useless. But nothing in the real world is perfectly reliable but we are still using many things and they are useful.
Also, the critics who said that Reagan would effectively revive an "offensive mode" of the arms races have ultimately been proved wrong. SDI is clearly a defense technology and while it temporarily led the Soviets to be even more offensive in their strategic planning, this had to collapse and this did collapse, leading the world to the end of the Cold War. I would summarize the U.S. critics' motivation by saying that the real reason why most of them were annoyed was that they wanted the Soviet Union to prevail and Reagan's plan made that outcome less likely. They were commies. In fact, Obama's administration is the first Democratic administration after Reagan that accepted that SDI is a good idea. Secretary of Defense Chuck Hagel proposed to increase the GBIs on Friday.
Before the SDI plans managed to undermine the Soviet empire, the CIA has played an effective misinformation game. The Soviets have spent lots of money on similar anti-rockets, too. X-rays were planned to be the defensive bullets. Most of these devices remained on paper but the implications of these papers were damn tangible and damn far-reaching.