Tamerlan and Dzhokhar Tsarnaev Illustration by Tom Bachtell

In the midst of the Second World War, Joseph Stalin, seized by one of his historic fits of paranoia and cruelty, declared the Chechen people disloyal to the U.S.S.R. and banished them from their homeland in the northern Caucasus to Central Asia and the Siberian wastes. Tens of thousands of Chechens, along with members of other small ethnic groups from the Caucasus and the Crimean Peninsula, died in the mass deportation or soon after—some from cold, some from starvation. The Tsarnaev family eventually settled in a town called Tokmok, in Kyrgyzstan, not far from the capital, Bishkek. Most who survived the next thirteen years in exile were permitted to return home, in the late fifties, under Nikita Khrushchev, and they reëstablished a sense of place as well as identity. Some remained expatriates. Chechens speak Russian with a thick accent; more often they speak their own language, Noxchiin Mott. The Caucasus region is multicultural in the extreme, but the predominant religion in the north is Islam. The Chechen national spirit is what is invariably called “fiercely independent.” When the Soviet Union collapsed, in 1991, nationalist rebels fought two horrific wars with the Russian Army for Chechen independence. In the end, the rebel groups were either decimated or came over to the Russian side. But rebellion persists, in Chechnya and in the surrounding regions—Dagestan and Ingushetia—and it is now fundamentalist in character. The slogan is “global jihad.” The tactics are kidnappings, assassinations, bombings.

Anzor Tsarnaev, an ethnic Chechen who lived much of his life in Kyrgyzstan, emigrated a decade ago to the Boston area with his wife, two daughters, and two sons. Despite arthritic fingers, he made his living as an auto mechanic. Members of the family occasionally attended a mosque on Prospect Street in Cambridge, but there seemed nothing fundamentalist about their outlook.

Anzor’s elder son, Tamerlan, appeared never to connect fully with American life. “I don’t have a single American friend,” Tamerlan told a photographer named Johannes Hirn, who asked to take pictures of him training as a boxer. “I don’t understand them.” He studied, indifferently, at Bunker Hill Community College, for an engineering degree. He described himself as “very religious”; he didn’t smoke or drink. Twenty-six and around two hundred pounds, he boxed regularly at Wai Kru Mixed Martial Arts. He loved “Borat” (“even though some of the jokes are a bit too much”). He had a daughter, but scant stability. Three years ago, he was arrested for domestic assault and battery. (“In America, you can’t touch a woman,” Anzor told the Times.)

David Bernstein, a retired mathematician from Moscow, who emigrated thirty-three years ago, said he knew the family because he used to take his car in regularly to Anzor. He noticed that Tamerlan sometimes worked at the body shop, although he didn’t seem happy about it. “I talked with Tamerlan about stupid things,” Bernstein recalled. “I asked him if he knew about his name, the great warrior. He talked a little about religion and politics. I said everyone is religious in a certain sense, and he said I should become a Muslim. I put him off, saying everyone invents his own religion.” When Bernstein discovered that his acquaintance was believed to be responsible for an act of terror at the finish line of the Boston Marathon, he was mystified. “I feel like Forrest Gump,” he said. “Suddenly, he is famous through this terrible act, and I had these conversations with him. But who can say they know him, really?”

Dzhokhar, nineteen, had graduated from Cambridge Rindge and Latin School, where he was a locally celebrated wrestler, described as slight, agile, and a little shy. He won a scholarship from the City of Cambridge. He worked for a couple of years as a lifeguard at a pool on the Harvard campus. A fellow-lifeguard remembered him as a “nice” kid with a “good sense of humor.” Dzhokhar’s high-school friends remembered him fondly, too. “He was a cool guy,” Ashraful Rahman said. “I never got any bad vibes from him. He wasn’t a star student, but he was smart. We met sometimes at the mosque in Cambridge. Dzhokhar went to the mosque more than I did, but he wasn’t completely devoted. When I think about this, I have to ask, was he forced to do this? Was he brainwashed? It’s so out of character. And you have to remember—he was a stoner. He was really into marijuana. And generally guys like that are very calm, cool.”

Essah Chisholm, a fellow-wrestler, said, “He was a cool dude.” But when Chisholm and a couple of his friends saw photographs of the Tsarnaev brothers on television Thursday night, they called the F.B.I. tip line. Late that night, the armed confrontation began—a shoot-out, a furious chase, hurled bombs. “It’s mind-boggling,” Chisholm said on Friday afternoon. “Every time I see his name on TV, it’s just unbelievable. To see Dzhokhar’s name, to see his face. I think this had to do with his older brother. Unless he was some sort of sleeper agent, I think his brother had a pretty strong influence. Tamerlan maybe felt like he didn’t belong, and he might have brainwashed Dzhokhar into some radical view that twisted things in the Koran.”

The sense of bland unknowingness—“He seemed so nice!”—began to evaporate the closer we got to the Tsarnaev brothers. Tamerlan’s YouTube channel features a series of videos in support of fundamentalism and violent jihad, including a rant by Feiz Muhammad, an Australian cleric and ex-boxer based in Malaysia; in one video, the cleric goes on about the evil “paganism” in the Harry Potter movies. Another video provides a dramatization of the Armageddon prophecy of the Black Banners of Khurasan, an all-powerful Islamic military force that will rise up from Central Asia and defeat the infidels; it is a martial-religious prophecy favored by Al Qaeda.

Dzhokhar’s Twitter feed—@J_tsar—is a bewildering combination of banality and disaffection. (He seems to have been tweeting even after the explosions at the finish line last Monday.) As you scan it, you encounter a young man’s thoughts: his jokes, his resentments, his prejudices, his faith, his desires.