What year do you think represents the high water mark for the former USSR? What events or factors can be cited in support?
In 1968 the cracks start showing rather plainly. Prague Spring and all that. The 70s were full of domestic problems, followed by the Soviet - Afghan War of the 80s and the disintegration of the Warsaw Pact in the late 80s-early 90s.
If revolts constitute cracks, then 1956 Hungary must have portended something bad.
I’d say somewhere between 12 April 1961, and 23 April 1967.
For quite a while they were well ahead of the US in space development, but then they started screwing up, and lost the lead, and never quite got it back.
Amongst many of the other reasons to think they’d peaked, this is probably the most publicly visible reason. Space was big propaganda, and they lost it.
The early to mid 1960s.
They had recovered from World War 2, living standards were rising.
Communism had adherents around the world, and they had gained an ally in Cuba, just a few miles from the U.S.
They were winning the space race, having launched the first satellite in 1957 and achieving a number of other “firsts”.
Maybe the launch of Sputnik and then the world’s first astronauts?
(on edit–I see I was ninja’ed by one minute!)
I would pick the late '50s to early-mid '60s, but for largely the same reasons.
While I agree that the reign of Sviatoslav I was a high point for the Kievan Rus’ and the introduction of Christianity has led to the long slide of decay and manipulation by the Orthodox churches, I think that’s probably digging a bit deep.
The Hungarian Revolution was due more to internal issues, albeit fed by alignment with Soviet policies by the compliant Rákosi regime. The Soviets were (rightly) concerned that if Hungary were allowed to take a separate path from the Warsaw Pact (as advocated by Nagy Imre) that it would have undermined the solidarity of the East Bloc nations, and the Soviets were particularly worried about Poland and East Germany coming under Western control for strategic reasons.
It is common to point to the Sputnik era and early successes in Soviet crewed spaceflight as a (technological) high point, but in fact they put comparably enormous resources into success with some fairly primitive technologies. “If it’s stupid but it works it’s not stupid” probably applies here but while the American ballistic missile and space exploration programs spurred on developments in integrated chip manufacturing, computing methods, commercial aerospace, et cetera the Soviet economy—which was almost entirely devoted to defense—did not reap such benefits.
Realistically, the Soviet Union and Russia in particularly never recovered demographically from World War II. While the United States had a post-war ‘baby boom’ and most of the rest of Western and Central Europe had a ‘baby bump’, the Russians never had a big population bloom, which was probably a good thing because they barely had the consumer industry to support the moderate population growth that they had. Actual census figures are unreliable but for the most part Soviet families barely reproduced at replacement levels while other developed nations were having large families and growing out into suburbia. Economically, real per capita growth in the USSR essentially peaked in the early Stalin era of 1924-1932 and ended with the Soviet, Kazakh, and and Ukrainian (Holodomor) famines in the early 1930s. The Soviet Union grew as a “Great Power” pre- and post-WWII by virtue of selling bountiful natural resources for pennies on the dollar, exploiting the slave labor of the GULAG system, and leaching off of its Warsaw Pact “client states” for economic viability.
Stranger
I’m not exactly sure what the data source is for this website but, based on this chart, I’d have to go with the NEP period:
Basically, for a short period after the Revolution but before starting to begin the Socialist/Communist policies, they simply had a non-imperial, relatively free market system where the government simply tried to rebuild the country and let people live peacefully.
That said, technology was better in the 1960s so the standard of living would still probably be higher in the USSR during that time period than during the NEP period. You were more likely to be locked up as a mental patient, though, if you weren’t willing to support the Communist party.
I read an interesting article once about the original Austin Mini. The design was groundbreaking, and should have been a huge success. But the British car industry was missing the dealer network, parts suppliers, and advertising that was necessary to really capitalize on it. Sounds like the Soviet space program of the early '60s was the same; great engineering, but without the ability to really take advantage of it.
Would have been about the same time, too. The Mini debuted in 1959.
From a sports point of view, I have often thought the year was 1976. I was living in Montreal then so paid a lot of attention to the Olympics. The Soviet Union and eastern bloc dominated. That was the year the East German women crushed everyone else in swimming, for example.
Of course, now we know that they were almost all doping. But back then all we had were suspicions.
By the time of the next non-boycotted games, in 1988, they were a shadow of what they had been.
Did gulag labor accomplish anything, like building tractors, or was it just punishment to keep comrades on the straight and narrow socialist path?
Yes. 
Pre-WWII, mostly mining and infrastructure. During the war it was a major source of labor for building arms and armaments. Post-WWII, a lot of Russian POWs who were repatriated, as well as people from the Baltics and the Ukraine that were blamed for not adequately performing during the war were shipped into the GULAG system. The system was never as productive as its increasingly ambitious goals but given the near-free cost of labor it was still an economic positive. After the Stalin-era the labor system was dismantled although a series of political education camps and closed cities were used to control dissidents.
Stranger
I’d say 1979.
The Soviet Union had just launched its coup/invasion of Afghanistan and nobody thought it would have much difficulty suppressing the insurgents. The Sandinistas took over Nicaragua and now a revolutionary Marxist regime shared a land border with the rest of Latin America, portending the export of revolution and guerilla warfare to the rest of the hemisphere. Cuban forces were fighting to uphold or install Marxist regimes in Africa. NATO planners were worried about the expansion and modernization of Warsaw Pact forces, while anti-nuclear pacifist protests seemed to herald the “Finlandization” of much of Europe. The USA was still reeling from its debacle in Vietnam and the oil and inflation shocks to the economy. The Ford and Carter administrations were seen as anemic. “Detente”, including opening sales of western wheat that propped up Soviet shortfalls, had been tried in the hopes of engaging the Soviet Union, to little outward moderation of USSR policies. As late as the mid-1980s science fiction writers were presuming that the “eastern bloc” would endure indefinitely. Pessimists predicted that the communist state would last 500 years.
Of course empires seem at their greatest just before the cracks appear, and the swiftness and completeness of the fall of the USSR still amazes people.
1920 - 22. Everything went downhill from then on. Slowly at fist, then very fast. And again. And again. With a couple of dead cat bounces. So I agree with Sage_Rat.
Not only was that not true, getting the Soviet Army mired in an insurgency in Afghanistan was all part of the plan:
I can’t speak to what “mid-1980s science fiction writers” and “pessimists” believed but economic analysts looking at Soviet dependency upon grain and basic consumer good imports (paid for by the extensive raw petroleum and natural gas export onto a market that was artificially amplified by the engineered scarcity of OPEC) knew that the the Soviet economy was terminally moribund. Although most predictions of failure were several decades into the future (as far as I can tell, Aleksandr Solzhenitsyn won the Showcase Showdown and even he didn’t think the USSR would fail before 2000) financial analysts familiar with the Soviet Union knew that the existing system could not continue indefinitely. Of course, the trifecta of Brezhnev—Andropov—Chernenko in progressive states of infirmity and near-death were not doing anything but continuing the policies of the Khrushchev era (eliminating the reforms he purportedly wanted to reference) and nothing changed until Gorbachev’s economic and political reforms…which ended up exacerbating the fundamental issues in the Soviet economy and accelerated the collapse.
Stranger
It was punishment (hard labor), but the labor was mostly useful. There was a lot of logging done (harvesting of natural resources) and construction of infrastructure, like the trans-Siberian railroad and various dams & bridges.
All very inefficient, but that’s typical of forced labor projects.
October 1962. The Cubans had not only established a Communist beachhead in the Western Hemisphere, they had repulsed a U.S. invasion. The Berlin Wall, despite being built to keep East Germans in, was an insult to the West. Then the USSR overstepped by putting missiles in Cuba. And they withdrew them without a shot being fired. Khrushchev failed to stop Brezhnev’s attempt to take over, and was deposed in 1964. It was a long, slow decline after that. Brezhnev lost power as his health declined. After he died, Andropov’s health failed, as well, and after that, Chernenko’s. Following three ailing leaders, Gorbachev’s legacy turned out to be overseeing the collapse of the USSR.
One odd curiosity from that era is the Order of Maternal Glory. The USSR gave medals to women who bore large families.