Shortly after eleven o’clock on the night of May 1st, two MH-60 Black Hawk helicopters lifted off from Jalalabad Air Field, in eastern Afghanistan, and embarked on a covert mission into Pakistan to kill Osama bin Laden. Inside the aircraft were twenty-three Navy SEALs from Team Six, which is officially known as the Naval Special Warfare Development Group, or DEVGRU. A Pakistani-American translator, whom I will call Ahmed, and a dog named Cairo—a Belgian Malinois—were also aboard. It was a moonless evening, and the helicopters’ pilots, wearing night-vision goggles, flew without lights over mountains that straddle the border with Pakistan. Radio communications were kept to a minimum, and an eerie calm settled inside the aircraft.

Fifteen minutes later, the helicopters ducked into an alpine valley and slipped, undetected, into Pakistani airspace. For more than sixty years, Pakistan’s military has maintained a state of high alert against its eastern neighbor, India. Because of this obsession, Pakistan’s “principal air defenses are all pointing east,” Shuja Nawaz, an expert on the Pakistani Army and the author of “Crossed Swords: Pakistan, Its Army, and the Wars Within,” told me. Senior defense and Administration officials concur with this assessment, but a Pakistani senior military official, whom I reached at his office, in Rawalpindi, disagreed. “No one leaves their borders unattended,” he said. Though he declined to elaborate on the location or orientation of Pakistan’s radars—“It’s not where the radars are or aren’t”—he said that the American infiltration was the result of “technological gaps we have vis-à-vis the U.S.” The Black Hawks, each of which had two pilots and a crewman from the 160th Special Operations Aviation Regiment, or the Night Stalkers, had been modified to mask heat, noise, and movement; the copters’ exteriors had sharp, flat angles and were covered with radar-dampening “skin.”

The SEALs’ destination was a house in the small city of Abbottabad, which is about a hundred and twenty miles across the Pakistan border. Situated north of Islamabad, Pakistan’s capital, Abbottabad is in the foothills of the Pir Panjal Range, and is popular in the summertime with families seeking relief from the blistering heat farther south. Founded in 1853 by a British major named James Abbott, the city became the home of a prestigious military academy after the creation of Pakistan, in 1947. According to information gathered by the Central Intelligence Agency, bin Laden was holed up on the third floor of a house in a one-acre compound just off Kakul Road in Bilal Town, a middle-class neighborhood less than a mile from the entrance to the academy. If all went according to plan, the SEALs would drop from the helicopters into the compound, overpower bin Laden’s guards, shoot and kill him at close range, and then take the corpse back to Afghanistan.

The helicopters traversed Mohmand, one of Pakistan’s seven tribal areas, skirted the north of Peshawar, and continued due east. The commander of DEVGRU’s Red Squadron, whom I will call James, sat on the floor, squeezed among ten other SEALs, Ahmed, and Cairo. (The names of all the covert operators mentioned in this story have been changed.) James, a broad-chested man in his late thirties, does not have the lithe swimmer’s frame that one might expect of a SEAL—he is built more like a discus thrower. That night, he wore a shirt and trousers in Desert Digital Camouflage, and carried a silenced Sig Sauer P226 pistol, along with extra ammunition; a CamelBak, for hydration; and gel shots, for endurance. He held a short-barrel, silenced M4 rifle. (Others SEALs had chosen the Heckler & Koch MP7.) A “blowout kit,” for treating field trauma, was tucked into the small of James’s back. Stuffed into one of his pockets was a laminated gridded map of the compound. In another pocket was a booklet with photographs and physical descriptions of the people suspected of being inside. He wore a noise-cancelling headset, which blocked out nearly everything besides his heartbeat.

During the ninety-minute helicopter flight, James and his teammates rehearsed the operation in their heads. Since the autumn of 2001, they had rotated through Afghanistan, Iraq, Yemen, and the Horn of Africa, at a brutal pace. At least three of the SEALs had participated in the sniper operation off the coast of Somalia, in April, 2009, that freed Richard Phillips, the captain of the Maersk Alabama, and left three pirates dead. In October, 2010, a DEVGRU team attempted to rescue Linda Norgrove, a Scottish aid worker who had been kidnapped in eastern Afghanistan by the Taliban. During a raid of a Taliban hideout, a SEAL tossed a grenade at an insurgent, not realizing that Norgrove was nearby. She died from the blast. The mistake haunted the SEALs who had been involved; three of them were subsequently expelled from DEVGRU.

The Abbottabad raid was not DEVGRU’s maiden venture into Pakistan, either. The team had surreptitiously entered the country on ten to twelve previous occasions, according to a special-operations officer who is deeply familiar with the bin Laden raid. Most of those missions were forays into North and South Waziristan, where many military and intelligence analysts had thought that bin Laden and other Al Qaeda leaders were hiding. (Only one such operation—the September, 2008, raid of Angoor Ada, a village in South Waziristan—has been widely reported.) Abbottabad was, by far, the farthest that DEVGRU had ventured into Pakistani territory. It also represented the team’s first serious attempt since late 2001 at killing “Crankshaft”—the target name that the Joint Special Operations Command, or JSOC, had given bin Laden. Since escaping that winter during a battle in the Tora Bora region of eastern Afghanistan, bin Laden had defied American efforts to trace him. Indeed, it remains unclear how he ended up living in Abbottabad.

Forty-five minutes after the Black Hawks departed, four MH-47 Chinooks launched from the same runway in Jalalabad. Two of them flew to the border, staying on the Afghan side; the other two proceeded into Pakistan. Deploying four Chinooks was a last-minute decision made after President Barack Obama said he wanted to feel assured that the Americans could “fight their way out of Pakistan.” Twenty-five additional SEALs from DEVGRU, pulled from a squadron stationed in Afghanistan, sat in the Chinooks that remained at the border; this “quick-reaction force” would be called into action only if the mission went seriously wrong. The third and fourth Chinooks were each outfitted with a pair of M134 Miniguns. They followed the Black Hawks’ initial flight path but landed at a predetermined point on a dry riverbed in a wide, unpopulated valley in northwest Pakistan. The nearest house was half a mile away. On the ground, the copters’ rotors were kept whirring while operatives monitored the surrounding hills for encroaching Pakistani helicopters or fighter jets. One of the Chinooks was carrying fuel bladders, in case the other aircraft needed to refill their tanks.

Meanwhile, the two Black Hawks were quickly approaching Abbottabad from the northwest, hiding behind the mountains on the northernmost edge of the city. Then the pilots banked right and went south along a ridge that marks Abbottabad’s eastern perimeter. When those hills tapered off, the pilots curled right again, toward the city center, and made their final approach.

During the next four minutes, the interior of the Black Hawks rustled alive with the metallic cough of rounds being chambered. Mark, a master chief petty officer and the ranking noncommissioned officer on the operation, crouched on one knee beside the open door of the lead helicopter. He and the eleven other SEALs on “helo one,” who were wearing gloves and had on night-vision goggles, were preparing to fast-rope into bin Laden’s yard. They waited for the crew chief to give the signal to throw the rope. But, as the pilot passed over the compound, pulled into a high hover, and began lowering the aircraft, he felt the Black Hawk getting away from him. He sensed that they were going to crash.

One month before the 2008 Presidential election, Obama, then a senator from Illinois, squared off in a debate against John McCain in an arena at Belmont University, in Nashville. A woman in the audience asked Obama if he would be willing to pursue Al Qaeda leaders inside Pakistan, even if that meant invading an ally nation. He replied, “If we have Osama bin Laden in our sights and the Pakistani government is unable, or unwilling, to take them out, then I think that we have to act and we will take them out. We will kill bin Laden. We will crush Al Qaeda. That has to be our biggest national-security priority.” McCain, who often criticized Obama for his naïveté on foreign-policy matters, characterized the promise as foolish, saying, “I’m not going to telegraph my punches.”

Four months after Obama entered the White House, Leon Panetta, the director of the C.I.A., briefed the President on the agency’s latest programs and initiatives for tracking bin Laden. Obama was unimpressed. In June, 2009, he drafted a memo instructing Panetta to create a “detailed operation plan” for finding the Al Qaeda leader and to “ensure that we have expended every effort.” Most notably, the President intensified the C.I.A.’s classified drone program; there were more missile strikes inside Pakistan during Obama’s first year in office than in George W. Bush’s eight. The terrorists swiftly registered the impact: that July, CBS reported that a recent Al Qaeda communiqué had referred to “brave commanders” who had been “snatched away” and to “so many hidden homes [which] have been levelled.” The document blamed the “very grave” situation on spies who had “spread throughout the land like locusts.” Nevertheless, bin Laden’s trail remained cold.

In August, 2010, Panetta returned to the White House with better news. C.I.A. analysts believed that they had pinpointed bin Laden’s courier, a man in his early thirties named Abu Ahmed al-Kuwaiti. Kuwaiti drove a white S.U.V. whose spare-tire cover was emblazoned with an image of a white rhino. The C.I.A. began tracking the vehicle. One day, a satellite captured images of the S.U.V. pulling into a large concrete compound in Abbottabad. Agents, determining that Kuwaiti was living there, used aerial surveillance to keep watch on the compound, which consisted of a three-story main house, a guesthouse, and a few outbuildings. They observed that residents of the compound burned their trash, instead of putting it out for collection, and concluded that the compound lacked a phone or an Internet connection. Kuwaiti and his brother came and went, but another man, living on the third floor, never left. When this third individual did venture outside, he stayed behind the compound’s walls. Some analysts speculated that the third man was bin Laden, and the agency dubbed him the Pacer.

Obama, though excited, was not yet prepared to order military action. John Brennan, Obama’s counterterrorism adviser, told me that the President’s advisers began an “interrogation of the data, to see if, by that interrogation, you’re going to disprove the theory that bin Laden was there.” The C.I.A. intensified its intelligence-collection efforts, and, according to a recent report in the Guardian, a physician working for the agency conducted an immunization drive in Abbottabad, in the hope of acquiring DNA samples from bin Laden’s children. (No one in the compound ultimately received any immunizations.)

In late 2010, Obama ordered Panetta to begin exploring options for a military strike on the compound. Panetta contacted Vice-Admiral Bill McRaven, the SEAL in charge of JSOC. Traditionally, the Army has dominated the special-operations community, but in recent years the SEALs have become a more prominent presence; McRaven’s boss at the time of the raid, Eric Olson—the head of Special Operations Command, or SOCOM—is a Navy admiral who used to be a commander of DEVGRU. In January, 2011, McRaven asked a JSOC official named Brian, who had previously been a DEVGRU deputy commander, to present a raid plan. The next month, Brian, who has the all-American look of a high-school quarterback, moved into an unmarked office on the first floor of the C.I.A.’s printing plant, in Langley, Virginia. Brian covered the walls of the office with topographical maps and satellite images of the Abbottabad compound. He and half a dozen JSOC officers were formally attached to the Pakistan/Afghanistan department of the C.I.A.’s Counterterrorism Center, but in practice they operated on their own. A senior counterterrorism official who visited the JSOC redoubt described it as an enclave of unusual secrecy and discretion. “Everything they were working on was closely held,” the official said.