In a 30-minute interview aboard Air Force One en route from Washington to Phoenix last Wednesday, President Obama talked with NEWSWEEK's Jon Meacham about Afghanistan, Iran, Israel, Pakistan, Dick Cheney—and Star Trek. Edited excerpts:

Meacham: The theme here is what you've learned. What's the hardest thing you've had to do?
The President: Order 17,000 additional troops into Afghanistan. There is a sobriety that comes with a decision like that because you have to expect that some of those young men and women are going to be harmed in the theater of war. And making sure that you have thought through every angle and have put together the best possible strategy, but still understanding that in a situation like Afghanistan the task is extraordinarily difficult and there are no guarantees, that makes it a very complicated and difficult decision.

Can anything get you ready to be a war president?
Well, I think that it certainly helps to know the broader strategic issues involved. I think that's more important than understanding the tactics involved because there are just some extraordinary commanders on the ground and a lot of good advisers who I have a lot of confidence in, but the president has to make a decision: will the application of military force in this circumstance meet the broader national-security goals of the United States? And you can't do that without understanding, let's say in Afghanistan, how that connects to Pakistan and what the nature of the insurgency there is, and what the history of the Soviet invasion was. So having some context, I think, is critical.

The other thing that's critical, I think, is having spent a couple of years on the campaign trail and then a number of years as a senator, meeting with young men and women who've served, and their families, and the families of soldiers who never came back, and knowing the price that's being paid by those who you're sending.

Can you talk about how you reached the surge decision?
I think the starting point was a recognition that the existing trajectory was not working, that the Taliban had made advances, that our presence in Afghanistan was declining in popularity, that the instability along the border region was destabilizing Pakistan as well. So that was the starting point of the decision.

We then embarked on a strategic review that involved every aspect of our government's involvement—Defense, State Department, intelligence operations, aid operations. Once that strategic review had been completed, then I sat in a room with the principals and argued about it, and listened to various perspectives, saw a range of options in terms of how we could move forward; asked them to go back and rework their numbers and reconsider certain positions based on the fact that some of the questions I asked could not be answered. And when I finally felt that every approach—every possible approach—had been aired, that all the questions had either been answered or were unanswerable, at that point I had to make a decision and I did.

Was the change-in-command decision that was made this week [Gen. David McKiernan was relieved as commander of the forces in afghanistan] part of the ongoing reaction to facts on the ground?
That is, I think, a reflection of a broader recognition that we have to apply some fresh eyes to the problem. General McKiernan has done an outstanding job; he's an outstanding military commander and has served his country with great distinction. But I have an obligation to make certain that we are giving ourselves the best possible opportunity to succeed, and at this moment there was a strong recommendation from the secretary as well as [Joint Chiefs of Staff] Chairman [Adm. Mike] Mullen that the team that we're now putting in place is best equipped to succeed.

Are you open to sending more troops in if this particular number can't make the progress you need to make?
I think it's premature to talk about additional troops. My strong view is that we are not going to succeed simply by piling on more and more troops. The Soviets tried that; it didn't work out too well for them. The British tried it; it didn't work. We have to see our military action in the context of a broader effort to stabilize security in the country, allow national elections to take place in Afghanistan and then provide the space for the vital development work that's needed so that a tolerant and open, democratically elected government is considered far more legitimate than a Taliban alternative. And the military component is critical to accomplishing that goal, but it is not a sufficient element by itself.

Moving to Pakistan, would you be willing to keep the option alive to have American troops secure those nuclear weapons if the country gets less stable?
I don't want to engage in hypotheticals around Pakistan, other than to say we have confidence that Pakistan's nuclear arsenal is safe; that the Pakistani military is equipped to prevent extremists from taking over those arsenals. As commander in chief, I have to consider all options, but I think that Pakistan's sovereignty has to be respected. We are trying to strengthen them as a partner, and one of the encouraging things is, over the last several weeks we've seen a decided shift in the Pakistan Army's recognition that the threat from extremism is a much more immediate and serious one than the threat from India that they've traditionally focused on.