Sasha Mordovets / Getty

In August, the Senate Intelligence Committee reported in exhaustive detail how Russia sowed division in the United States and sought to meddle in the 2016 election in favor of Donald Trump. Immediately, Republicans and Democrats battled over whether the Trump campaign had engaged in a “criminal conspiracy” with Russia, or “collusion,” or “cooperation,” or established “ties”—or whether, as the White House claimed, Trump was the victim of a massive liberal conspiracy. Years after 2016, Russian election interference continues to reap dividends for Moscow by turning American against American.

Russian President Vladimir Putin is particularly adept at psychological warfare because he has been practicing it for decades. He learned the art of destabilizing his opponents from the Stasi, East Germany’s secret police. Russia now uses the same techniques. However, it not only targets individuals; it torments entire countries.

In the late 1980s, Putin lived in Dresden, East Germany. On paper, he ran a Soviet-German “friendship house.” In practice, he was a KGB agent, likely helping the Red Army Faction, a left-wing terrorist group, plot attacks in West Germany. The KGB was eager to learn surveillance techniques from the Stasi, and Putin worked closely with the organization (researchers recently discovered Putin’s Stasi card).

Throughout the ’70s and ’80s, East Germany worked to repress dissidents, artists, peace campaigners, and church activists. The regime was worried, however, that the usual authoritarian strategies—gulags, physical torture, and tanks on the streets—might damage the country’s reputation. After all, East Germany had promised to uphold human rights as a signatory of the 1975 Helsinki Accords. But East German leader Erich Honecker wasn’t concerned about suppressing the opposition: “There will always be the Stasi.”

The East German secret police developed a method known as Zersetzung or “decomposition” to stamp out rebellion without the use of overt force. The idea was to chip away at a dissident’s sanity so that he would lose the will to resist, or in the words of a Stasi guide, “[provoke] and [enforce] internal conflicts and contradictions within hostile-negative forces that fragment, paralyze, disorganize, and isolate” the opponent. The first step in a campaign was to identify the target’s weak spots—health, family, finances—then strike them over and over. Stasi agents might break into a dissident’s apartment and move the pictures around or change the time on the alarm clock. They might mail a sex toy to a target’s wife or send postcards from an unknown woman demanding child support. They might enlist doctors to give false medical diagnoses or ensure that a manager halted the dissident’s career progress without explanation. The techniques were targeted, flexible, and above all efficient.

Decomposition was designed to unglue a dissident’s psyche. A regime opponent would find himself trapped in a Kafkaesque nightmare. Everywhere he turned, an evil force seemed to be hounding him, even though he could not prove that he had been singled out. Who would believe that the government was secretly stealing his dish towels? Some targets suffered breakdowns and others killed themselves. The writer Jürgen Fuchs, a Stasi victim, called the campaign “an assault on the human soul.”

In recent years, Russia has reportedly used the methods of decomposition against individual journalists and diplomats. Putin’s real innovation has been to weaponize Zersetzung against countries. Much of Moscow’s foreign policy can be understood as a kind of diplomatic decomposition, a grand strategy of gaslighting. After all, Putin faces the same fundamental problem as the East German leadership: how to suppress opposition without overt violence. Moscow wants to restore Russia as a great power and reverse the tide of Western encroachment. But in today’s world of integrated global economies and nuclear deterrence, open aggression is extremely costly—which is why conventional wars between countries are very rare. The answer to this conundrum lies with the Stasi playbook, employed on a much grander scale.

Russia seeks to weaken a foreign adversary from the inside, paralyzing its ability to resist. It partners with a range of allies, such as oligarchs and journalists, and uses a diverse toolbox, including propaganda and cyber attacks. Moscow begins by locating the target country’s weakest point, whether it’s an ethnic, religious, or partisan cleavage. Then Russia manufactures a sense of distrust to destroy the social contract. Whereas the Stasi might break into a man’s apartment in the middle of the night and turn on his electric razor—just to freak him out—Moscow uses hackers and trolls to propagate conspiracy theories and cultivate a skepticism of authority.

Russia’s meddling in the 2016 U.S. election was less about altering the result, and more about messing with America’s sanity—feeding cynicism about the system, encouraging people to second-guess reality, and leaving America too incapacitated to offer much resistance. Since 2016, the Kremlin has continued trying to maximize political division, using troll farms and Facebook to boost both Trump and Bernie Sanders, and attack Joe Biden.

Putin also tried to decompose the European Union by backing far-right nationalist parties such as the French National Rally (formerly the National Front) and the Alternative for Germany, as well as the Leave campaign in the Brexit referendum. Moscow spread false reports of rape by immigrants in Berlin—a classic decomposition technique. Russian operatives were linked to a plot to undermine the parliamentary election in Montenegro in 2016, and stop the Balkan country from entering NATO. (Montenegro eventually joined the alliance in 2017.)

Modern-day Russia isn’t the only country that has tried to destabilize an enemy. Long before Putin came to power, the Soviet Union engaged in what were known as “active measures.” During the Cold War, Moscow spread the rumor that the U.S. government created AIDS as a secret biological weapon. Meanwhile, the United States used Radio Free Europe to sow opposition against communist regimes behind the Iron Curtain.

Russia’s weaponized Zersetzung is unusual, however, in its calibrated use of pressure and its keen awareness of the enemy’s weak spots, especially the vulnerability of democratic societies in an age of social media, populism, and distrust of elites. Just like the Stasi sought to destroy a target’s reputation by blending accurate and damaging information with harmful lies, so Russian media mixes real stories with disinformation to make people doubt the truth, or as the Russian state television network RT slogan says, “Question More.” For its part, Moscow claims that its actions are a defensive measure against Western efforts to decompose Russia and depicts all independent reporting at home as foreign-backed psychological warfare.

Trump is unable to resist Russia’s strategy because he refuses to criticize Putin. But the issue goes beyond Trump: Countering Russia’s tactics would be tough even if the United States had a leader who took the danger seriously. Biden has promised that “if any foreign power recklessly chooses to interfere in our democracy, I will not hesitate to respond as president to impose substantial and lasting costs.” But checking Russia will be easier said than done because of America’s stark polarization. The Russian threat has become yet another partisan issue. Even if Biden wins in November, he could face Republican opposition to any tough response. And although economic sanctions might hurt Russia’s economy, they won’t easily heal the divisions that weaponized decomposition has deepened in America. Putin’s assault on the national soul is working.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.