But what’s arguably a bigger deal, and what’s been overshadowed in all the coverage of the haggling over this interim pact, is just how momentous these last several months have been for U.S.-Iranian relations. Since Iranian President Hassan Rouhani took office this summer, the two countries have engaged in the highest-level talks since the 1979 Iranian Revolution, first through a meeting between Zarif and Secretary of State John Kerry, and then through a phone call between Rouhani and President Obama (the two had previously exchanged letters). Zarif has also pioneered a new approach to speaking directly to the American people, turning to social-media outlets like Twitter and YouTube to defend, in English, Iran’s positions at the Geneva negotiations.

The way the news cycle works these days, we take it for granted that Kerry is now in Geneva celebrating a diplomatic breakthrough with Zarif. But the frenzied diplomacy this fall has truly been exceptional. As the Ploughshares Fund’s Joe Cirincione remarked after nuclear talks collapsed earlier this month, Kerry and Zarif “spent more time [together] in the last 24 hours than they have in 34 years.”

Nothing drives this point home more than David Crist’s The Twilight War, which chronicles America’s failures, over three decades, to communicate with Iran—and the grave risks this state of affairs has posed for war by miscalculation. “With no diplomatic ties and only occasional meetings in dark corners of hotel bars and through shadowy intermediaries, neither side has an accurate view of the other,” Crist, a Pentagon historian, wrote. In other words, we’ve been living through another cold war—but one without a proverbial “red phone.”

The nadir in this “twilight war,” at least symbolically, came on a Monday evening in February 1990, when President George H.W. Bush, desperate to free American hostages in Lebanon, spoke for 29 minutes on the phone with a man he believed to be then-Iranian President Hashemi Rafsanjani. Only later did Bush learn that the person on the other end of the line was an Iranian who opposed Rafsanjani’s outreach to the United States and wanted to embarrass the Iranian leader. The lines of communications between the two countries were so frayed that the president of the United States fell for a prank call.

But the examples don’t stop there. The history of the relationship is littered with unrequited outreach, abortive low-level diplomatic encounters, byzantine communications channels, and two-timing intermediaries. During his first term, Ronald Reagan sent three letters on White House stationery via foreign ministers from other countries to the Iranian government in an effort to improve bilateral relations, never receiving a response (the Iranians weren't sure the letters were authentic). After American officials—secretly spirited to Tehran on board a CIA-piloted Israeli aircraft—failed to strike a weapons-for-hostages deal in 1986, Reagan took to his diary to vent his frustration. “It seems the rug merchants and the Hisballah [sic] would only agree to 2 hostages,” the president wrote. “This was a heartbreaking disappointment for all of us.” In 1999, Bill Clinton grew so frustrated with his administration’s thwarted overtures to President Mohammad Khatami that he loitered around the U.N. General Assembly after Khatami’s address in the hopes of bumping into the reformist Iranian leader. Khatami ducked out a side entrance.