(Although I would argue that Mikhail Gorbachev is probably more to be praised for the fall of the Soviet Union than Reagan.)
I'd note that Gorbachev had no intention of presiding over the end of the USSR or the end of Communist monopoly rule thereof. He believed it was possible to moderate the regime and allow enough partial openness to let them continue forever. (He also seems to have hoped that the Warsaw Pact nations would remain in the USSR's sphere of influence voluntarily, and ditto the internal Soviet republics-- though in the event, he wasn't unwilling to send tanks into Lithuania, for example.) For whatever it's worth, Reagan's vision seems to have been clearer on this point than Gorbachev's, and the pressure he placed on the regime seems to be a major reason for this. (There were certainly forces in the US that wanted to help the Soviets keep things together, in the name of the perpetual State Department goal of "stability". Fortunately, by the time George H.W. Bush was in place to actively try to implement this-- sticking with Gorbachev even after it was clear that Yeltsin was the future and telling the Ukrainians to sit tight-- it was too late.)
Now, maybe it was sheer coincidence that we got what Reagan wanted (and was talking about at least as early as 1981), and not what Gorbachev wanted (right up to the day that it was explained to him that since he'd never had popular support, the 1991 coup's demonstration that he also lacked military and KGB support meant his services were no longer necessary). But when someone sets a grand strategic goal, pursues policies aimed at that goal, sees that goal achieved, and finds both participants in and victims of the defeated regime crediting/blaming him for it, I'm inclined to give him the benefit of the doubt. Someone like Gorbachev was certainly necessary (though Reagan had to wait through more Russian leaders than any other President before Gorbachev showed up). But with a detente-minded US President willing to perpetuate the 70's military establishment indefinitely (or to cut it further, in line with our lessened horizons), I see no reason the Soviets couldn't have held on. With no expensive military challenges, no loud demands for freedom, no fierce condemnations of the system-- all those provocative things that only a crazed or simpleminded warmonger would resort to in international diplomacy-- and with a general expectation that things would remain more or less as they had been, the people and governments of the Iron Curtain alike might well have muddled through the 80s much as they did the 70s, secure in the knowledge that any loss of confidence and capability on their part was being matched on ours. 1989 might simply have been another 1981, 1968, or 1956.
I know that's what I was expecting, right up through 1989. After all, as a friend noted, "It's not as if they're dancing on the Berlin Wall." Except that on November 11, 1989, two and a half years after Reagan had issued a widely derided challenge to Gorbachev to "tear down this wall"-- with the only Soviet response being a complaint that he'd given "an openly provocative, war-mongering speech"-- they were.
I don't dispute that a Gorbachev was necessary. But it would be hard, given Gorbachev's own statements, strategies, and actions, to show that a Gorbachev without a Reagan would have been sufficient.
Re: Legacies
I'd note that Gorbachev had no intention of presiding over the end of the USSR or the end of Communist monopoly rule thereof. He believed it was possible to moderate the regime and allow enough partial openness to let them continue forever. (He also seems to have hoped that the Warsaw Pact nations would remain in the USSR's sphere of influence voluntarily, and ditto the internal Soviet republics-- though in the event, he wasn't unwilling to send tanks into Lithuania, for example.) For whatever it's worth, Reagan's vision seems to have been clearer on this point than Gorbachev's, and the pressure he placed on the regime seems to be a major reason for this. (There were certainly forces in the US that wanted to help the Soviets keep things together, in the name of the perpetual State Department goal of "stability". Fortunately, by the time George H.W. Bush was in place to actively try to implement this-- sticking with Gorbachev even after it was clear that Yeltsin was the future and telling the Ukrainians to sit tight-- it was too late.)
Now, maybe it was sheer coincidence that we got what Reagan wanted (and was talking about at least as early as 1981), and not what Gorbachev wanted (right up to the day that it was explained to him that since he'd never had popular support, the 1991 coup's demonstration that he also lacked military and KGB support meant his services were no longer necessary). But when someone sets a grand strategic goal, pursues policies aimed at that goal, sees that goal achieved, and finds both participants in and victims of the defeated regime crediting/blaming him for it, I'm inclined to give him the benefit of the doubt. Someone like Gorbachev was certainly necessary (though Reagan had to wait through more Russian leaders than any other President before Gorbachev showed up). But with a detente-minded US President willing to perpetuate the 70's military establishment indefinitely (or to cut it further, in line with our lessened horizons), I see no reason the Soviets couldn't have held on. With no expensive military challenges, no loud demands for freedom, no fierce condemnations of the system-- all those provocative things that only a crazed or simpleminded warmonger would resort to in international diplomacy-- and with a general expectation that things would remain more or less as they had been, the people and governments of the Iron Curtain alike might well have muddled through the 80s much as they did the 70s, secure in the knowledge that any loss of confidence and capability on their part was being matched on ours. 1989 might simply have been another 1981, 1968, or 1956.
I know that's what I was expecting, right up through 1989. After all, as a friend noted, "It's not as if they're dancing on the Berlin Wall." Except that on November 11, 1989, two and a half years after Reagan had issued a widely derided challenge to Gorbachev to "tear down this wall"-- with the only Soviet response being a complaint that he'd given "an openly provocative, war-mongering speech"-- they were.
I don't dispute that a Gorbachev was necessary. But it would be hard, given Gorbachev's own statements, strategies, and actions, to show that a Gorbachev without a Reagan would have been sufficient.