In the U.S. I was taught that we won the cold war. This was because of the large increase in military defense spending by the U.S. government and while the Soviets tried to keep up they eventually went bankrupt leading to their downfall and the "fall of communism". Was this really the main factor? We're there more important factors that I wasn't taught? Or were there smaller, but also important factors leading to the fall of the Soviet Union?
Stephen Kotkin's Apocalypse Averted: The Soviet Collapse 1970-2000 is a good and highly readable summary of this period.
In short, while the arms race was indeed a heavy burden on the Soviet economy (they were spending over 20% of their budget on defense to try to maintain parity with a USA spending merely 5% of its budget), that wasn't the most or even one of the most important factors in the collapse according to Kotkin.
Kotkin's premise relies on the contention that the Soviet economy, built around heavy industry and factories built in the 1930s-1950s was turning into "the world's largest Rust Belt," filled with outdated industry working on outdated machinery to churn out the needs of a bygone age, increasing steel production and other heavy industry goals while the West swung to consumer needs. The Soviet economy was artifically propped up in the late 70s/early 80s by the oil shock, which drove world oil prices to then-record highs and allowed the USSR to camoflague its economic woes through selling oil. When the price of oil collapsed and lost 2/3rds of its value in 1985-6, the USSR was left holding the bag.
Kotkin also argued that the dismantling of the Soviet state ideology by Gorbachev led to a devestating crisis in confidence in the state. Free(ish) press, relaxed censorship, and a more open economy led to uncomfortable questioning of the perviously silenced horrors and atrocities of the Stalin era, which undermined the Soviet people's confidence in the Communist Party. Gorbachev's fantasy of converting the USSR into a multi-party democracy met the rather humbling realization that the Communist Party wasn't as popular as it imagined. National elites in some (though not all) of the republics plotted secession. In Russia itself, Boris Yeltsin led a bizarre but popular effort to pull Russia itself out of the USSR. Gorbachev's power declined by the day. The crisis met a hed in August 1991 when hardliners in the Soviet military attempted a coup to stabilize the crumbling USSR. The coupsters abducted and imprisoned Gorbachev and declared themselves in supreme power. Yeltsin led a protest that showed that even rank and file soldiers didn't sympathize with the coup, and Gorbachev was freed.
After the coup there was no serious hope of preserving the USSR and the Soviet republics all seceded by New Years of 1992. Gorbachev, totally superfluous as head of a nonexistent country, resigned.