The nail-biting, 40-minute clandestine operation that resulted in Osama bin Laden's death could have been a calamitous political and military failure; a bloodbath in Pakistan that left scores of civilians dead and U.S. forces killed or captured by America's most ferocious enemy.
Or, as it happened, it could unfold largely in textbook fashion — delivering a stunning success for the often maligned intelligence community, a political and national security coup for a struggling president and revenge for Americans still carrying vivid memories of Sept. 11, 2001.
By secretly sending a team of special operations forces into an enemy fortress in a suburban neighborhood of a sovereign country, President Barack Obama chose the path of greatest risk, but also greatest reward.
As debates continued over whether a photograph of bin Laden's body should be released; if Pakistan had helped the al-Qaida leader elude capture and whether he had to be shot after it was revealed he was unarmed, an expert said there were many ways the operation could have gone wrong.
As U.S. officials evaluated their options ahead of the raid, Obama asked for a gut check from top members of his national security team.
The various plans, White House counterterror chief John Brennan said, were "debated across the board and the president wanted to make sure, at the end, that he had the views of all."
The level of risk stretched from moderate to massive.
'Fog of war'
"When you go into something like this, there are no guarantees," said Dick Couch, a Navy SEAL during the Vietnam War who later worked for the CIA. "There's the fog of war. Things go wrong that you don't really plan or intend."
Bin Laden might not have been there, the commandos could have run into stiff resistance or hidden explosives, or U.S. troops might have been detected by Pakistani forces who could have taken action against them, Couch said in a phone interview Tuesday.
"They have to plan ahead and account for as many of these contingencies as possible," he added. "But you can't take all the risk out of it."
An airstrike, like the one that killed al-Qaida in Iraq leader Abu Musab al-Zarqawi in an Iraq safe house in June 2006, could be done quickly, from a drone or bomber far away, generating little risk for U.S. troops.
In that operation, U.S. special operations forces went in after the F-16 strike and collected documents, electronic storage devices and weapons that were hidden under the floorboard in the building.
But that safe house was in a war zone where U.S. forces were already engaged.
Still, a bombing brings its own shortcomings: a misfire, an aircraft problem, the potential for widespread civilian casualties and difficulty in identifying enemy remains obliterated in a missile strike.
Putting troops on the ground in Pakistan was by far the most dangerous option — both militarily and politically.
While an ally, Pakistan is a sovereign nation that has complained bitterly about U.S. drone strikes targeting insurgents within its borders. And Islamabad officials have strongly resisted having U.S. combat troops on Pakistani soil.
Obama knew that anything short of a clean and victorious mission would have dire consequences — further eroding an already tenuous relationship with Pakistan during a critical period of the Afghanistan war.
The U.S. needs Pakistan's assistance rooting out terrorists along the border and helping to prevent militants from crossing into Afghanistan as they become more active in the warmer spring weather.
At the same time, a helicopter assault that dropped elite commandos into the bin Laden compound forced them into direct combat, putting American lives in greater danger and presenting a greater risk of aircraft or equipment failures.
It also required exhaustive planning and training, which provided greater chances for information to leak out over the ensuing months, scuttling the mission and sending bin Laden deeper into hiding.
The benefits, however, were too rich to ignore. With a precision assault, there would be much greater certainty the commandos would positively identify bin Laden — a linchpin for success.
It also reduced the risk of mass civilian casualties and dramatically increased the opportunity to gather what officials call a treasure trove of documents and intelligence.
As he reviewed the options, Obama had history to consider. As some of his predecessors can attest, these are the missions that can define a presidency.
President Jimmy Carter's failed re-election bid was blamed in part on the disastrous attempt to rescue American hostages from the U.S. Embassy in Tehran in 1980.
Eight American troops were killed when a special operations aircraft collided with a Navy helicopter at a rendezvous point in the desert on their way to the embassy.
And in the 1993 Battle of Mogadishu, made famous in the movie "Black Hawk Down," two helicopters were shot down and 18 American soldiers were killed during a U.S. mission to snatch a Somali clan warlord.
The same kind of helicopters were used in the bin Laden raid.
The images of gunmen dragging the bodies of U.S. soldiers through Mogadishu's dusty streets became an icon for those opposed to U.S. involvement overseas.
President Bill Clinton ordered a U.S. withdrawal and promised to never again deploy troops unless there was a clear U.S. national interest.
Did Pakistan help bin Laden?Meanwhile Thursday, Pakistan was facing growing pressureto explain how the world's most-wanted man was able to live for years in the military garrison town of Abbottabad, just north of Islamabad.
The White House has vowed to "get to the bottom" of whether Pakistan helped bin Laden.
Pakistan has welcomed bin Laden's death, but its foreign ministry expressed "deep concerns" about the raid, which it called an "unauthorized unilateral action."
The CIA said it kept Pakistan out of the loop because it feared bin Laden would be tipped off, highlighting the depth of mistrust between the two supposed allies.
The revelation that bin Laden was unarmed appeared to contradict an earlier account from a U.S. security official that bin Laden "participated" in the firefight.
White House spokesman Jay Carney on Tuesday cited the "fog of war" as a reason for the initial misinformation.
If this becomes controversial, it could complicate U.S. efforts to mend ties with the Muslim world in the wake of the wars in Afghanistan and Iraq.
Carney insisted bin Laden resisted during the raid, although he would not say how.
"There was concern that bin Laden would oppose the capture operation and, indeed, he resisted," Carney said. "A woman ... bin Laden's wife, rushed the U.S. assaulter and was shot in the leg but not killed. Bin Laden was then shot and killed. He was not armed."
While many world leaders applauded the U.S. operation that killed bin Laden, there were concerns in parts of Europe.
"It was quite clearly a violation of international law," former West German Chancellor Helmut Schmidt told German TV. "The operation could also have incalculable consequences in the Arab world in light of all the unrest."
Geoffrey Robertson, a prominent London-based human rights lawyer, said the killing "may well have been a cold-blooded assassination" that risked making bin Laden a martyr.
"It's not justice. It's a perversion of the term. Justice means taking someone to court, finding them guilty upon evidence and sentencing them," he told the Australian Broadcasting Corp.
U.S. officials were also wrestling with whether to release graphic photographs of bin Laden's body, which could provide proof of his death but risks offending Muslims.
"It's fair to say that it's a gruesome photograph," Carney said.