A few years old, but new to me: an interesting perspective from Yegor Gaidar, reformist economist of the post-Gorbachev era. • Collectivisation and urbanization left the Soviet Union with a grain shortfall. Rather than reform the agricultural sector, they paid for food with oil exports.

• In the 1985, the Saudis decided they would no longer act as swing producer and forgo exports while other members of OPEC cheated. The Saudis started a price war and broke up the cartel. Oil went briefly under $10 a barrel and Soviet oil revenue dried up.

• At first the Soviets paid for food with foreign reserves, then they borrowed. But then they began to reach the limits of their credit.

• Part of Gorbachev’s reforms were with the idea of becoming a country the West would lend to, even provide state guarantees in exchange for reform.

That didn’t work out too well. As Brzezinski later said, the Soviet Union could be an empire or a democracy, but not both. Once they showed weakness, everyone wanted out.