MUCH AS HE RUES the death of the Soviet Union, President Vladimir Putin will never manage to resurrect it. Nonetheless, the Russian leader, unafraid to twist arms in what he regards as Moscow’s strategically critical backyard, has scored a victory — and dealt the West a major defeat — by squashing Ukraine’s hopes of integration with Europe.

Bowing to months of muscle flexing by Russia, Ukraine announced Thursday that it would suspend long-standing efforts to join a trade and political association with the European Union, which was to be finalized this week. Instead, Ukraine, a country of 46 million people with extensive industrial and agricultural resources, said it will begin talks to join a customs union dominated by Moscow.

This may not be the end of the story. But if Ukraine, long divided between East and West, fails to draw closer to Europe, it will not only be a setback for the European Union, which has pressed for years to bring Ukraine into a formal alliance. It’s also a crushing disappointment to millions of Ukrainians, especially younger ones, who hoped for a future in a country energized by Western investment and anchored by values of transparency, pluralism, rule of law and judicial independence. Ukrainian opponents of the decision immediately staged street protests.

Casting its lot with Russia, on the other hand, will mean declining investments and a deepening economic crisis. As Swedish Foreign Minister Carl Bildt said: “They are not going West. I don’t think they are going East. I feel they are going down.”

Granted, the Ukrainian president, Viktor Yanukovych, faced a difficult calculus. Signing up for association with the E.U., and the possibility of full membership down the road, offered the prospect of modernization, investments and, probably, a major economic aid package from the International Monetary Fund (IMF). On the other hand, the IMF deal would have compelled Mr. Yanukovych to adopt a punishing austerity program that could have complicated his reelection in 2015.

It was also widely assumed that the E.U., as a condition of finalizing its pact with Ukraine, would have required Mr. Yanukovych to release from prison his bitter political rival, former prime minister Yulia Tymoshenko , who is serving a seven-year sentence on trumped-up charges. Ms. Tymoshenko had been expected to go to Germany for medical treatment; now her prospects are unclear.

In the end, the decisive factor for Ukraine appeared to be Russian blackmail. Among other sanctions, Moscow threatened to cut off imports from companies in eastern Ukraine, which relies heavily on Russian markets. To force its neighbors to heel, Russia is more than willing to make them suffer.

Using similar scare tactics, Mr. Putin also derailed Armenia’s talks with the E.U. a few months ago. Two other small former Soviet republics have defied him; despite the threat of Russian retribution, Georgia and Moldova are expected to join the E.U. association this week. Just as in Soviet times, Moscow’s muscle-flexing can compel obedience from some of its neighbors, some of the time. No matter how it may try, though, it cannot compel respect, let alone friendship.