The US was initially planning a massive air strike using B-2 Spirit bombers to level the Abbottabad hideout of Osama bin Laden but chose an assault by its elite commandos who killed the world's most wanted terrorist a year ago.
In his tell-all account, Matt Bissonnette, a Navy SEAL who participated in Operation Neptune Spear to kill the top al-Qaeda leader in Pakistan, says that President Barack Obama and his advisors discussed different options till the last moment.
"The president still had not signed off on the ground- assault option. All we had been authorised to do up to now was to start planning and conduct rehearsals. The White House was still considering an Air Force option, a massive air strike using B-2 Spirit bombers to level the house," writes Bissonnette in No Easy Day: The Autobiography of a Navy SEAL using the pseudonym "Mark Owen".
He says Defence Secretary Robert Gates supported the air strike because it kept American ground forces out of Pakistan, which made the mission less like an invasion of the country's sovereignty.
The air strike option required 32 2000-pound smart bombs.
"The barrage would last for a full minute and a half and the crater would penetrate at least 30 feet into the earth in case the compound had a bunker system. The possibility for collateral damage was high, and the possibility of finding identifiable remains after that kind of destruction was low."
The just-released book, published by Penguin, gives fascinating details of the mission undertaken by 22 SEALS, an EOD tech and a CIA interpreter, who flew in two Black Hawk helicopters into Abbottabad, where Pakistan's military academy is located, on the night of May 2, 2011 from a US base in Jalalabad. They killed Osama and four others hiding in a house.
Recalling how Osama was killed, the book says the point man's shots had entered the right side of the al-Qaeda leader's head and blood and brains spilled out of the side of his skull.
He writes that Osama perhaps knew "we were coming" when he heard the helicopter.
"Bin Laden had more time to prepare than the others, and yet he still didn't do anything. Did he believe his own message? Was he willing to fight the war he asked for? I don't think so. Otherwise, he would have at least gotten his gun and stood up for what he believed."
Osama also wasn't even prepared for a defence.
"He had no intention of fighting. He asked his followers for decades to wear suicide vests or fly planes into buildings, but didn't even pick up his weapon," the book says.
The assault by SEALS and explosion of one of their helicopters at the target compound close to Pakistan's military academy finally attracted the attention of the country's Air Force.
"Unknown to us, they grounded all their aircraft and started a head count. With everyone accounted for, they scrambled two F-16 fighters armed with 30 mm cannons and air-to-air missiles. Pakistan's military has always maintained a state of high alert against India. Most of the country's air defences are aimed east toward that threat. The jets roared into the sky and raced toward the Abbottabad area."
The book, co-authored by journalist Kevin Maurer, has irked the Pentagon which has threatened to take legal action against Owen on charges of leaking classified information.
Owen says his goal was to "tell the true story of the raid and show the sacrifices made by the SEALs at the command. I only used my life as a way to describe what it is like to be part of such a special unit".
He also claims that till date, how the mission to kill Osama has been reported is wrong.
"Even reports claiming to have the inside story have been incorrect. I felt like someone had to tell the true story. To me, the story is bigger than the raid itself and much more about the men at the command who willingly go into harm's way, sacrificing all they have to do the job. Theirs is a story that deserves to be told, and told as accurately as possible."