Transcript for Former Secretary of Defense Ash Carter one-on-one
God next up two or more of our conversation with former Defense Secretary ash Carter who came in today he is a new book out. Called inside the five sided box lessons from a lifetime of leadership inside the Pentagon it's a fascinating read asked him. About the biggest threats facing our country the necessity of a space force the controversy over transgender us troops in the military. And what it's like to lead one of the biggest agencies and all of government. You speak about national security threats in the book you've actually like a good. Military guy have an acronym for address ER I KT. China Russia Iran North Korea terrorism. The five biggest guns which formed were you. Most when you well you to listen to talk about Sierra in Haiti which the military units. Usual way turn him in Akron amendment. Possible one cricket. It was just why a very simple way of saying here are today's problems we need to be ready in an answer your question which is the worst. You can eat we got a dual five oh. And if you think about it each of those five is focused only on us they only have one problem. We have five story that doesn't talk about the future and if you're the secretary defense in this sector defensive today he always got to remember tomorrow as well as the space forces that I will that's an example. I would take him manager. I want Astra way parenthetically President Obama was attracted pace forced to. And he kept coming back to us tonight enthusiastic about creating a separate lives alone in dealing several meat or so. In which he's actions we. Space force. And I always said no I think the other and I argued for another managerial approach and he would. Except that but I do want to ask about North Korea the president current president president trump has been repeatedly claiming that the administration was awfully close to war. With North Korea in fact just yesterday he said it looked like it was going to be war with North Korea when I took over as president everybody knows that he's the. True. I don't wouldn't say it was close to war I would say that. North Korea was. Plummeting pell mell forward with its nuclear program something needed to be done about that. We did not conduct negotiations. With North Korea. My approach was deterrence. And defense. Building missile defenses strengthening our forces strengthening South Korean forces so that north -- would always know that if it started anything. It's military would be destroyed and its regime would be destroyed and their certainty that to that approach to bail them to me. Well we didn't of the war in that sense of succeed you heard it it it it. Did not turn back their nuclear program. In his interview with with George Stephanopoulos yesterday the president. Was asked if a foreign country approached him with some. Information or his democratic opponent. What would he do we see cure them out. EU CE danger in that. Yeah I think. President of United States in any matter ought to be relying upon information provided by. Or forward he says its foreign governments every day we course you talked for an. Powers everything you need in need Butte they tell you things and sometimes you believe him some times you. You don't but when it comes to domestic politics. My answer would be. Look we'll talk about firm policy but amok and talk about American politics with union forum leader. You were also the secretary who lifted the military's ban on trans gender service members which was you were hailed for significant decision that you know this person's reversed it. Just last week he said of transgender service members they take massive amounts of drugs you're not allowed to take drugs. One to ask but that surely you heard those counter argue that the time had. To overcome your mind you things partisan character and that none of this is there something in in the air we have an all volunteer force and we need to get good people. And what matters is military qualifications. Everything else is social policy military policy. Is to get the best qualified people that's the basis of everything I did. In personnel now with respect transgender at all I'd said that if transgender members were to be accessed to the US military. They had to be stable in their new gender does what I announced at the time for eighteen months before we would take them. Because we weren't gonna. Take them readiness. And cost implications. Of this switches the medical point I think we've been referred to your book. He it's quite a sweeping in detailed look at what it takes to run. A man. Organization in fact very early in the book you talk about the number of people that you had reporting to you. As secretary that the Defense Department employs more people than Amazon McDonald's FedEx target NGE. Combined line half the federal budget was under your control what was the secret to being successful leader that. They Defense Department thrives on clarity. Inconsistencies seen need to be very clear and I always choose my words very carefully I'd write my own statements if we were doing something new. So that everything was just right the other thing is to make people and their field families feel good about what they're doing so I wanna talk to troops. I would always do two things one was to tell them their mission and how important it was strategically but the other one was to say you were doing most noble thing. And a young person can do. With your life. Our thanks again to ash Carter for that conversely.
This transcript has been automatically generated and may not be 100% accurate.