At his dacha, standing before a map of the newly expanded Soviet Union shortly after Germany’s surrender in May 1945, Josef Stalin nodded with approval. The vast buffer he’d carved out of Soviet-occupied Eastern Europe would now protect his empire against future Napoleons and Hitlers. Stalin then took the pipe from his mouth, waving it under the base of the Caucasus. He shook his head and frowned.

“I don’t like our border right here,” he said to his aides, gesturing at the area where the Soviet republics of Georgia, Armenia, and Azerbaijan met the hostile powers of Turkey and Iran.

Over the next year and a half, U.S.-Soviet relations would collapse as Stalin pressured Ankara and Tehran for territorial concessions and U.S. President Harry S. Truman pushed back by sending a naval flotilla to the Mediterranean. In February 1947, a penniless Britain told the State Department that it could no longer defend the Greek government in its civil war with Yugoslav-backed Communist rebels, prompting Truman to pledge U.S. economic and military aid for Athens and Ankara. Stalin, whose country was struggling to recover from Nazi devastation, fell back on defense. His aim now would be to hold the new security zone in Eastern Europe and to prevent the United States from controlling Russia’s mortal enemy: Germany.

In March 1947, the new U.S. secretary of state, George C. Marshall, embarked on six grueling weeks of negotiations in Moscow with his Soviet counterpart, Vyacheslav Molotov, over the future of occupied Germany. With neither side willing to accept the possibility of such a dangerous, strategically situated country becoming an ally of the other, the talks ended in stalemate. Yet Stalin still believed that Truman would ultimately be compelled to concede German unification on Soviet terms — massive reparations and a political structure favorable to the Communists — in order to fulfill his predecessor Franklin D. Roosevelt’s pledge to withdraw U.S. troops from Europe within two years after the war.

Marshall left Moscow convinced that cooperation with the Soviets was over. Germany, and much of Western Europe, was edging toward economic and social collapse, and the Leninist dictum “the worse, the better” appeared to be Stalin’s response. The time had come, Marshall decided, for unilateral U.S. action to secure democratic, capitalist government in the parts of Europe still outside Soviet control. In an iconic speech at Harvard University on June 5, 1947, he presented the outline of what would become a massive four-year U.S. aid scheme to support European reconstruction and integration: the Marshall Plan.

Stalin denounced the plan as a vicious American plot to buy political and military domination of Europe. He feared losing control not just of Germany but of Eastern Europe, too. Prior to the launch of the Marshall Plan, Stalin had never been dogmatic about the forms of socialism pursued by countries within the Soviet sphere. Bulgaria, Czechoslovakia, Hungary, Poland, and Romania were all allowed to form coalition governments of one sort or another. His demand had merely been fealty to Moscow on foreign policy. That would soon change. By the end of 1948, Stalin had fully co-opted or crushed the remaining non-Communist elements in the governments of Eastern Europe.

Truman had wanted to use the Marshall Plan as a tool to reduce U.S. security entanglements in Europe. But the State Department had conditioned the $13.2 billion (more than $135 billion in today’s money) in grants on the recipients integrating their economies, leaving them to object that the loss of self-sufficiency would make them more vulnerable to Soviet (and German) harassment and threats. So the president now acceded to French and British demands that Marshall aid be given a military escort. On April 4, 1949, a year and a day after signing the Marshall aid legislation, Truman signed the founding agreement of the North Atlantic Treaty Organization (NATO).

The following month, the United States, Britain, and France accepted the constitution for a new West German state. The Soviets responded by creating their own East German state in October. The dialectic of each side’s suspicions of the other having played out as far as it could without war, the European borders of the Cold War conflict would remain frozen for the next 40 years.

West Berliners crowd in front of the Berlin Wall as they watch East German border guards demolishing a section of the wall in order to open a new crossing point between East and West Berlin, near the Potsdamer Square on Nov. 11 1989 . (Gerard Malie/AFP/Getty Images)

Four decades later, on Nov. 9, 1989, frenzied East German crowds gathered at the Berlin Wall yelling “Tor auf!” (“Open the gate!”). When a worried and confused border guard complied, tens of thousands began pouring into the West. Millions more would do so in the coming days.

In Dresden six weeks later, a crowd greeted West German Chancellor Helmut Kohl shouting “Einheit! Einheit! Einheit!” (“Unity!”). Nearby, a nervous but determined 37-year-old KGB officer had spent weeks burning mounds of documents in preparation for possible attacks on his station by angry mobs. The enormous volume of ash destroyed the building’s furnace. Years later, Russian journalists interviewed the former officer about his work in Germany. “We were interested in any information about the main opponent,” Vladimir Putin explained. That opponent, NATO, would continue to obsess Russian leaders in the years to come.

By early 1990, the East German Communists, imploding under the weight of popular revulsion and infighting, were a spent political force, and Soviet General Secretary Mikhail Gorbachev had begun to reconcile himself to German unification. What he still demanded was that a reunified Germany not be part of the Atlantic alliance. Continued German membership of NATO, Gorbachev told German and Soviet journalists, must be “absolutely ruled out.”

Gorbachev and his Russian successors have maintained that they were misled over whether the alliance would be permitted to expand eastward. NATO, the Soviet leader said, was “an organization designed from the start to be hostile to the Soviet Union.” “Any extension of the zone of NATO,” he told then-U.S. Secretary of State James Baker, would therefore be “unacceptable.” Yet when Germany reunified in October, he was powerless to stop the eastern part from exiting the Warsaw Pact and entering NATO.

With the demise of Gorbachev and the Soviet Union in 1991, Russian President Boris Yeltsin continued to press the issue with his American counterpart. The United States, he told then-President Bill Clinton, was “sow[ing the] seeds of distrust” by dangling NATO membership in front of former Warsaw Pact states. For a Russian leader to “agree to the borders of NATO expanding toward those of Russia,” he told Clinton during a 1995 meeting at the Kremlin, “would constitute a betrayal of the Russian people.” Defense Minister Pavel Grachev warned Polish leaders that his countrymen saw the alliance as a “monster directed against Russia.” Foreign Intelligence Service head Yevgeny Primakov, who would later become foreign minister and prime minister, argued that NATO expansion would necessitate a more robust Russian defense posture. “This is not just a psychological issue for us,” he insisted to the U.S. diplomat Strobe Talbott in 1996. “It’s a security question.” Moscow’s Council on Foreign and Defense Policy warned that NATO enlargement would make “the Baltic states and Ukraine … a zone of intense strategic rivalry.”

Russia’s resistance left Clinton two sensible options. He could ignore it and insist on expanding NATO in a robust way, under the logic that “Russia will always be Russia” and would harass and dominate its neighbors if not contained by the threat of military force. This was the Republican position at the time, outlined in the party’s 1994 “Contract with America.” The other was to sit tight until Russian behavior belied its pledges to respect its neighbors’ sovereignty. This was former Ambassador to the Soviet Union George Kennan’s position. But Clinton, being Clinton, chose a third option, which was to expand NATO on the cheap — under the logic that the alliance faced no real enemy. In 1996, Ronald Asmus, soon to become an influential Clinton administration official, argued that NATO expansion costs would be modest since the “premise [was] avoiding confrontation with Russia, not preparing for a new Russian threat.”

“Are we really going to be able to convince the East Europeans that we are protecting them,” asked an incredulous Democratic Sen. Sam Nunn in a speech to military officials, “… while we convince the Russians that NATO enlargement has nothing to do with Russia?” Talbott warned in an internal memo that “An expanded NATO that excludes Russia will not serve to contain Russia’s retrograde, expansionist impulses.” On the contrary, he argued, “it will further provoke them.” But Richard Holbrooke, then Clinton’s special envoy to the Balkans, dismissed this warning. The United States, he wrote in World Policy Journal in 1998, could “have [its] cake and eat it too … years from now … people will look back at the debate and wonder what all the fuss was about. They will notice that nothing has changed in Russia’s relationship with the West.”

Holbrooke could not have been more wrong. “We have signed up to protect a whole series of countries,” the 94-year-old Kennan told the New York Times columnist Tom Friedman in 1998, “even though we have neither the resources nor the intention to do so in any serious way.” He would prove right. Clinton’s gambit would pit an under-resourced NATO against an ever-more embittered and authoritarian Russia.

Days after the Czech Republic, Hungary, and Poland joined NATO in March 1999, the alliance began a three-month bombing campaign against Serbia — which, like Russia, is a Slavic Orthodox state. These attacks on a brother country appalled ordinary Russians, especially since they were not carried out in defense of a NATO member, but to protect the Muslim population of Kosovo, then a Serbian province. NATO’s actions in the former Yugoslavia — in Bosnia in 1995 as well as in Serbia in 1999 — were undertaken with noble aims: to stop the slaughter of innocents. NATO expansion into the former Warsaw Pact countries, however, all but guaranteed that Russians wouldn’t see them that way. Moscow knew that its former vassals, by joining the alliance, had now bound themselves to support Western policies that challenged Russian interests. The farther east NATO expanded, the more threatening it would become.

That seemed especially clear when NATO members began taking unilateral actions hostile to Russia, actions they would never have taken outside the alliance. In 2015, for example, Turkey shot down a Russian fighter jet that had crossed into its airspace from Syria, where it was bombing opponents of the Bashar al-Assad regime. “Turkish airspace … is NATO airspace,” the Turkish foreign ministry pointedly told Russia after the attack. Russia took notice. “Turkey has set up not itself” as the actor, “but the North Atlantic alliance as a whole,” said Prime Minister Dmitry Medvedev in an interview with Time magazine. “This is extremely irresponsible.”

Crimeans wave Russian flags as they celebrate the first anniversary of the referendum on March 16, 2015 in Sevastopol, Crimea. (Alexander Aksakov/Getty Images)

In trying to assure the Russians that NATO was not a threat, the Clinton administration had taken it for granted that legitimate Russian interests, in an era following glasnost and perestroika, would not clash with NATO interests. But this view presumed that the Cold War had been driven by ideology and not geography. Halford Mackinder, the father of geopolitics, would have scoffed at this view. Mackinder, who died in 1947, the year the Truman Doctrine and the Marshall Plan were launched, drew policymakers’ attention to the strategic centrality of the vast Eurasian “Heartland,” which was dominated by Russia. “Who rules East Europe,” he famously wrote in 1919, “commands the Heartland; Who rules the Heartland commands the World-Island; Who rules the World-Island commands the World.” It was the ideas of Mackinder, and not Marx, that best explained the Cold War.

Russia’s eternal fear of invasion drove its foreign policy then and continues to do so now. “At bottom of [the] Kremlin’s neurotic view of world affairs is [a] traditional and instinctive Russian sense of insecurity,” Kennan wrote in his famous 1946 Long Telegram. Vast, sparsely populated, and with huge transport challenges, Russia had a natural tendency to fracture. Looking outward, Russia was a “land which had never known a friendly neighbor.” Its defining characteristic was its indefensibility. No mountain ranges or bodies of water protected its western borders. For centuries, it suffered repeated invasions. That landscape and history encouraged the emergence of a highly centralized and autocratic leadership obsessed with internal and external security. Communists had been just one variety of such leadership, peculiar to the age in which they emerged.

The country’s western borders have always been particularly vulnerable. The European landmass west of Russia’s borders constitutes a large peninsula surrounded by the Baltic and North Seas to the north, the Atlantic Ocean to the west, and the Black Sea to the south. Russia, in contrast, has few maritime outlets. The Arctic Ocean is remote from its population centers. The country’s few ports are largely unusable in the winter. Turkish waters to the south, like Nordic waters to the north, can be easily blocked. During the Cold War, Norwegian, British, and Icelandic airbases also hindered Russian access to the sea.

But such problems were not limited to the 20th century. In the latter half of the 19th century, Russia had been contained by France and Britain — in the Balkans, the Middle East, India, and China — well before Kennan made “containment” a household word. Its defensive options being limited, its military doctrine has historically been offensive. It has sought to dominate its neighbors as a means of preventing the borderlands from being used against it by other powers. Whereas the West sees Russia’s fear of invasion as groundless, history has shown Russian leaders that foreign intentions are typically hidden or fluid. Each age brings a new existential threat; there would always be another Napoleon or Hitler.

After World War II, the threat was, from the Kremlin’s perspective, capitalist encirclement led by Washington and its West German puppet. The incorporation of Ukraine and Belarus (1922) and the Baltic countries (1940) into the Soviet Union, and the creation of buffer states farther east, bolstered Russia’s security at the expense of the West’s. In 1949, splitting control of Germany created a stable equilibrium, one that survived four decades. Once Moscow lost control of Berlin in 1989, however, Russia’s defensive frontier collapsed, forcing it to retreat to borders farther east than they had been since the 18th century.

In his 2005 state of the nation address, Russian President Vladimir Putin, the former KGB officer who had been on the front lines of Moscow’s covert efforts against NATO during the 1980s, described the collapse of the Soviet Union as the “greatest geopolitical catastrophe” of the 20th century. Much of his long tenure as president has been devoted to restoring elements of the Soviet Union’s economic space and security frontier in the face of NATO and European Union expansion — and preventing the old Soviet empire’s constituent parts from undermining the interests of today’s Russia.

While military conflicts in Moldova, Georgia, and Ukraine have been attributed to aggressive Kremlin efforts to re-establish elements of the Soviet empire, it is notable that Russia has not annexed any of the breakaway regions — with the exception of Crimea, which houses the Russian Black Sea Fleet. The reason is not merely deniability, but also the fact that annexation of pro-Russian territories would have strengthened the pro-Western forces in the remaining parts of each country. Annexation would undermine Russia’s primary objective, which is keeping the countries beyond the reach of Western institutions seen to threaten Russian interests. The presence of frozen conflicts in the three nations effectively blocks them from joining NATO. The alliance has always rejected aspirants with unresolved border disputes, internal territorial conflicts, and insufficient military capacity to provide for a credible national defense.

In the cases of Georgia and Ukraine, the timing of the Russian interventions coincided with those countries’ achievement of tangible benchmarks on the path to NATO membership. The combined separatist territories, under effective Russian control, now form a valuable protective arc along Russia’s western and southwestern border. Just as Stalin strengthened the Soviet Union’s buffer zone in response to the Marshall Plan, which he expected Washington to supplement with military force, Putin has strengthened Russia’s buffer zone in response to NATO expansion.

Putin’s views are perhaps best captured by a private conversation he had with the former Israeli leader Shimon Peres shortly before the latter’s death, in 2016. “What do [the Americans] need NATO for?” Peres recalled him asking. “Which army do they want to fight? They think I didn’t know that Crimea is Russian, and that Khrushchev gave it to Ukraine as a gift? I didn’t care, until then you needed the Ukrainians in NATO. What for? I didn’t touch them.”

These are not the words of an ideologue. Nor are they a reflection of a uniquely ruthless Russian leader. After all, Gorbachev, no fan of Putin’s, also supported the annexation of Crimea, as well as Russian military action in Georgia. The West, he wrote in his memoirs, had been “blind to the kind of sentiments NATO expansion aroused” in Russia.

Western leaders do not need to sympathize with Russia, but if they wish to make effective foreign policies, they do need to understand it. Communism may have vanished from Europe, but the region’s geography has not changed. Russia is, as it has always been, too large and powerful to embed within Western institutions without fundamentally changing them and too vulnerable to Western encroachment to acquiesce in its own exclusion.

The Marshall Plan, which cemented the Cold War, is remembered as one of the great achievements of U.S. foreign policy not merely because it was visionary but also because it worked. It worked because the United States accepted the reality of a Russian sphere of influence into which it could not penetrate without sacrificing credibility and public support.

Great acts of statesmanship are grounded in realism no less than idealism. It is a lesson America needs to relearn.

The excerpt was adapted from Benn Steil’s new book The Marshall Plan: Dawn of the Cold War.