There are still plenty of key details that haven’t been released about the raid on bin Laden’s compound. This in turn has led to understandable speculation — for instance, about which Navy Seal might have shot bin Laden and under precisely what conditions. But there’s another mystery, much less talked about, that is arguably far more important and may hold clues to just how tough a call this operation was.

It has to do with the size of the force sent into Abbottabad. We know that 79 American commandos in four helicopters — two Blackhawks and two modified MH-47 Chinooks — took part in the operation. We’ve been told a fair amount about the actions of the 24 Seals who descended into the compound in the two Blackhawks (one of which malfunctioned and had to be destroyed). Little information, however, has been released about the other 56 Seals who were riding in those Chinooks. What, exactly, were they doing there?

A widely-read tick-tock piece from The New York Times last week offers some explanation as to their purpose: “A ‘fight your way out’ option was built into the plan, with two helicopters following the two main assault copters as backup in case of trouble.” But that begs the question: what kind of trouble was expected?

I spoke to a former counter-terrorism official with long experience overseeing special operations about this question. Here’s what he told me:

We know the CIA was watching that house for months. They knew who was in there: two guys, bin Laden’s couriers, some women and children, and they hoped bin Laden himself. That’s about it. Now for a raid like that you would typically send in ten to twelve Seals. Many more than that and it actually complicates the operation. They sent in nearly 80. That is highly unusual. That’s enough to start a small war. Those two mopes inside just didn’t constitute a threat requiring 80 Seals.

And those Chinooks are not part of the standard package for these tier one units. They’re not stealthy, not very maneuverable. Small arms fire or an RPG can take one of those things out if they’re hovering. A Chinook is only used if you need to ferry 30 or 40 guys.

What this tells me is that those 56 Seals were most likely brought in on those Chinooks to set up a perimeter around the compound or to be on station somewhere nearby to take on any security forces that might have been there to protect bin Laden. We knew bin Laden has no security inside that house, other than the two mopes. But it’s right in the heart of the Pakistani military. So we had some idea of who might be protecting him. And you had to plan for the worst.

So imagine Obama is in the Situation Room being briefed by the head of JSOC, and he’s told ‘We don’t want another Black Hawk Down. If we go in we’re going to make sure we can fight our way out. And that could mean a whole lot of Pakistani military casualties.’ And in such a scenario when things really went bad, you have to assume there was an AC130 gunship on station that would have been called in. That’s an incredibly lethal platform. It would be standard operating procedure, just part of the doctrine, to have one nearby for close air support.

And the president said yes to that. Fortunately everything went more or less according to plan. But you look at the force package we went in with — that footprint is the story. It speaks to the downside risk and concerns they had. And it means the decision Obama made was even gutsier than people realize. He was basically risking a small war with Pakistan.”

Paul Glastris

Paul Glastris is the editor in chief of the Washington Monthly. A former speechwriter for President Bill Clinton, he is writing a book on America’s involvement in the Greek War of Independence.