It’s not that the FSB, the major Russian intelligence agency, has never been able to work with its American counterparts. The most romantic period of their relationship was in 2013, following the April 15 Boston Marathon bombings, which killed three people and injured some 250. Two brothers from the Russian republic of Chechnya, Dzokhar and Tamerlan Tsarnaev, had organized the attack, and it became known soon afterward that the Russian FSB had sent messages in 2011 to the FBI and CIA about Tamerlan Tsarnaev. Though these letters were not real warnings—the FSB asked for information on him, fearing he could join a militant group—the information inflamed public opinion in the United States, and there were calls for more cooperation between Russian and American intelligence agencies. Russian President Vladimir Putin and U.S. President Barack Obama spoke twice by phone in the wake of the bombing. A White House statement said Obama praised the “close cooperation” Washington received on counterterrorism from Moscow, and that “both sides underlined their interest in deepening” it. Congressmen rushed to Moscow praising FSB’s willingness to work together.

It had long been assumed that militants in the North Caucasus were not interested in attacking Western targets. After the 1990s, the Chechen movement shifted from what had been a primarily nationalist agenda to make Chechnya independent, to one embracing radical Islam. Militants continued to employ a terrorist strategy against the Russians—including attacking civilians in Moscow, and killing law-enforcement personnel in the North Caucasus. But foreigners had not been in their crosshairs. Ahead of the 2014 Olympics in Sochi, at the foot of the Caucasus Mountains near the Islamists’ stronghold, the Boston bombing raised questions about whether that had changed.

Yet within a month after the Boston bombings, the FSB arrested Ryan Christopher Fogle, a third secretary in the political section of the U.S. embassy. The FSB alleged he was a CIA officer and accused him of trying to recruit an FSB counterterrorism officer who was involved in Russia-U.S. counterterrorism cooperation. The Russian agency wanted to make the lesson and the story public—a colorful video with a confused Fogle wearing a ludicrous wig was shown on Russian TV, and the diplomat was thrown out of the country. The counterterrorism officers in the FSB quickly learned the possible costs of close cooperation with the Americans.