The violent final minutes were the culmination of years of intelligence work. Inside the CIA team hunting bin Laden, it always was clear that bin Laden's vulnerability was his couriers. He was too smart to let al-Qaeda foot soldiers, or even his senior commanders, know his hideout. But if he wanted to get his messages out, somebody had to carry them, someone bin Laden trusted with his life.
In a secret CIA prison in Eastern Europe years ago, al-Qaeda's No. 3 leader, Khalid Sheikh Mohammed, gave authorities the nicknames of several of bin Laden's couriers, four former U.S. intelligence officials said. Those names were among thousands of leads the CIA was pursuing.
One man became a particular interest for the agency when another detainee, Abu Faraj al-Libi, told interrogators that when he was promoted to succeed Mohammed as al-Qaeda's operational leader, he received the word through a courier. Only bin Laden would have given Libi that promotion, CIA officials believed.
If they could find that courier, they'd find bin Laden.
The revelation that intelligence gleaned from the CIA's so-called black sites helped kill bin Laden was seen as vindication for many intelligence officials who have been investigated and criticized for involvement in a program that involved the harshest interrogation methods in U.S. history.
"We got beat up for it, but those efforts led to this great day," said Marty Martin, a retired CIA officer who for years led the hunt for bin Laden.
Mohammed did not reveal the names while being subjected to the simulated drowning technique known as waterboarding, former officials said. He identified them many months later under standard interrogation, they said, leaving it once again up for debate as to whether the harsh technique was a valuable tool or an unnecessarily violent tactic.
It took years of work for intelligence agencies to learn he was a Kuwaiti-born man named Sheikh Abu Ahmed.
When they did identify him, Ahmed was nowhere to be found. The CIA's sources didn't know where he was hiding. Bin Laden was famously insistent that no phones or computers be used near him, so the eavesdroppers at the National Security Agency kept coming up cold.
Then, in the middle of last year, the courier had a phone conversation with someone who was being monitored by U.S. intelligence, according to an American official, who like others interviewed for this story spoke only on condition of anonymity. The courier was located somewhere away from bin Laden's hideout when he had the discussion, but it was enough to help intelligence officials locate and watch him.
Last August, the courier unknowingly led authorities to a compound in the northeast Pakistani town of Abbottabad, where Libi had once lived. The walls surrounding the property were as high as 18 feet. Nobody patrolled the compound in Abbottabad. In fact, nobody came or went. And no telephone or Internet lines ran from the compound.
The CIA believed that bin Laden was hiding in plain sight, in a hideout especially built to go unnoticed. But it wasn't sure. Despite the uncertainty, intelligence officials saw this as the best chance to get to bin Laden. They decided not to share the information with anyone, including NATO allies.
By mid-February, officials were convinced a "high-value target" was hiding in the compound. President Obama wanted to take action.
"They were confident and their confidence was growing: 'This is different. This intelligence case is different. What we see in this compound is different than anything we've ever seen before,' " John Brennan, the president's top counterterrorism adviser, said Monday. "I was confident that we had the basis to take action."
Options were limited. The compound was in a residential neighborhood in a sovereign country. If Obama ordered an air strike and bin Laden was not in the compound, it would be a huge diplomatic problem.
"The president had to evaluate the strength of that information, and then made what I believe was one of the most gutsiest calls of any president in recent memory," Brennan said.
Obama tapped two dozen members of the Navy's elite SEAL Team Six to carry out a raid with surgical accuracy.
About 12:45 a.m. Monday, Pakistani time, two helicopters entered Pakistani airspace using sophisticated technology intended to evade that country's radar systems.
The helicopters lowered into the compound, dropping the SEALs behind the walls. No shots were fired, but shortly after the team hit the ground, one of the helicopters came crashing down and rolled onto its side for reasons the government has yet to explain. None of the SEALs were injured, however, and the mission continued.
With the CIA and White House monitoring the situation in real time, presumably by live satellite feed or video carried by the SEALs, the team stormed the compound.
Thanks to sophisticated satellite monitoring, U.S. forces knew they would likely find bin Laden's family on the second and third floors of one of the buildings on the property, officials said. The SEALs secured the rest of the property first, then proceeded to the room where bin Laden was hiding. In the ensuing firefight, Brennan said, bin Laden used a woman, believed to be one of his wives, as a human shield. She was wounded.
The SEALs killed bin Laden with a bullet to the head.
The body was immediately identifiable, but U.S. officials also conducted DNA testing that identified him with near 100 percent certainty, senior administration officials said.
"I think the accomplishment that very brave personnel from the United States government were able to realize yesterday is a defining moment in the war against al-Qaeda, the war on terrorism, by decapitating the head of the snake known as al-Qaeda," Brennan said.
U.S. forces searched the compound and flew away with documents, hard drives, and DVDs that could provide valuable intelligence about al-Qaeda, a U.S. official said. The entire operation took about 40 minutes, officials said.
Bin Laden's body was flown to the USS Carl Vinson in the north Arabian Sea, where officials conducted a traditional Islamic burial ritual at sea. Bin Laden's body was washed and placed in a white sheet. He was placed in a weighted bag that, after religious remarks by a military officer, was slipped into the sea about 2 a.m. EDT Monday.
Said the president: "I think we can all agree this is a good day for America."