Iran’s deal with the members of the U.N. Security Council and Germany survived Israeli, Republican and Arab criticism over an endless nuclear-themed summer. As the fight continues, the debate can only be improved with a deeper historical understanding of the difficulties the nations have in friendship, spying and deal-making in the nuclear age.

Conveniently, “Deutschland 83” — a well-reviewed, little-watched summer series on SundanceTV — serves up three lessons from the early Reagan years for today’s nuclear politics in the form of an edutaining spy thriller.

Inspired by Soviet fears that NATO was planning a nuclear attack in the early 1980s, “Deutschland 83” spins a tale about a young East German border guard shanghaied by his aunt, a member of the Stasi, East Germany’s version of the KGB, into impersonating an aide-de-camp to a West German general. The series follows the young spy’s struggles against the Stasi’s morose humanity, which combines with its outsized power over the lives of others into a bumbling logic that threatens to bring about nuclear war.

Lesson 1: Being friends can be harder than being enemies

The show’s dramatic complexity comes from the historical reality that there was just as much tension and misunderstanding within the blocs as between them. Meeting at the Cold War’s front line, the two Germanies depended on their respective superpower patrons for security.

The road to the nuclear brink started with a hardware upgrade. Since the late 1970s, the Soviets had been replacing the missiles targeting Western Europe with a more accurate model that was faster to launch.

This made European governments, and West Germany especially, nervous — because the United States and the Soviet Union were roughly equal in the damage they could inflict upon their respective homelands as a result of a nuclear deal they had struck. Would NATO’s localized nuclear inferiority in Europe invite a Soviet attack?

President Carter’s administration did not share European concerns. Long before Israeli Prime Minister Benjamin Netanyahu mounted a public campaign against U.S. nuclear negotiations and interjected himself on the losing side of a presidential election, West German Chancellor Helmut Schmidt gave public speeches about the risks of U.S.-Soviet nuclear talks and advocated for Gerald Ford’s reelection.

Schmidt’s agitation bore fruit as a new NATO policy. The alliance pledged to match Soviet missiles while simultaneously pursuing arms control negotiations with the enemy.

That solution created new problems among the NATO allies. Majorities in Western Europe were against the deployment of NATO missiles, resulting in large protests that accepted the story of NATO as the aggressor. East Germany was happy to lend the peace movement support, a historical fact reflected well in the series.

Inside the Warsaw Pact, East Germany had to be more creative in bending Moscow’s policies to its own interests. The relationship also created incentives among German bureaucrats to gain favor with the Soviets.

While their alliances with their superpower patrons were strained, the two Germanies shared a powerful and pure interest in avoiding nuclear war on their soil. “Deutschland 83” luxuriates in the smallness and intimacy of two Germanies, each with their complicated patron-client relationships.

Lesson 2: Good spycraft is more than stealing secrets

“Deutschland 83” shows that a spy agency that excels at stealing the enemy’s secrets can still be misled by its own preconceptions and paranoia.

The Soviets could not — would not — believe U.S. public explanations about why it was fielding new nuclear capabilities in Europe. “Deutschland 83” picks up there, with the Stasi’s foreign intelligence service sending the fictional protagonist to gather intelligence on NATO missile deployment and purposes.

Was the West preparing for a nuclear first strike? Soviets suspicion had its reasons.

First, the West was installing a nuclear capability entirely consistent with a surprise attack.

Second, U.S. leadership addressed the Soviet Union with aggressive rhetoric and was challenging its government’s legitimacy — and that of its close allies.

Third, only a naif would forget the lessons of Western perfidy after Nazi Germany misled the Soviets and attacked.

If the Soviet paranoia still sounds ludicrous, try proper nouns in the news today. Is Iran hell-bent on getting a nuclear arsenal?

First, Iran was installing a nuclear infrastructure entirely consistent with a weapons program.

Second, its leadership addresses the United States with aggressive rhetoric and challenges its government’s legitimacy — and that of its close allies.

Third, only a naif would forget the lessons of dictators’ perfidy after Nazi Germany misled the West and attacked.

It is difficult to cross-check evidence about countries’ intentions and capabilities against one another without getting trapped in circularity. Tasking spies to find evidence of an impending nuclear attack without asking for disconfirming information can lead to deeply flawed analysis.

How did the Soviets know that the United States intended to attack? NATO was deploying a new nuclear missile capability that could be used in a first strike. And how did the Soviets know that the missiles were intended for a first strike? According to Soviet doctrine, the U.S. regime was by nature aggressive.

Lesson 3: Nuclear deals are morally and strategically ambiguous

That same circular logic appears in some arguments about Iran. How do we know Iran will cheat on a nuclear deal? Iran has developed uranium enrichment capabilities that could be used to build nuclear arms. And how do we know that the enrichment capability will be used in a weapons program? The Iranian regime is by nature aggressive.

Judging the P5+1’s nuclear deal with Iran based on the regime’s trustworthiness or other moral qualities is similarly circular. If a country has never played with its nuclear options, there is no sense in striking a deal.

Whether it is a bad or good deal depends on how well the proposed monitoring and enforcement system will detect Iranian attempts to circumvent it. Regrettably, commentators and politicians comfortable condemning the Iranian regime outnumber those willing and able to spend time on the technical details.

The NATO-Soviet nuclear crisis was eventually resolved through a nuclear deal in 1987 that removed both sides’ missiles. That treaty included a formal monitoring process, as well as a method for clarifying compliance and investigating the allegations of violations.

A Hollywood ending, then? No, more of an ambiguous European art-house fin. Last summer, the United States officially accused Russia of violating that treaty. Should the possibility of cheating more than 15 years later have stopped Reagan from making the deal?

Alex Bollfrass is a fellow at the Stimson Center and a security studies PhD candidate at Princeton University.