Chuck Hagel, a former U.S. defense secretary, talks about President Donald Trump's first year and leadership approach.

WASHINGTON — From 1997 to 2009, Chuck Hagel represented the state of Nebraska as a Republican member of the U.S. Senate. After a few years off, he returned to public service as the 24th secretary of defense, serving under President Barack Obama from 2013-2015, a tumultuous period that saw the rise of the Islamic State group and the spread of great-power competition.

Hagel recently sat down with Defense News to discuss the state of the world and his views on President Donald Trump. For more from Hagel, including videos from the interview, visit DefenseNews.com.

What’s your view on how President Trump has done through his first year?

I think he’s done great damage to the presidency, his leadership to our country. He, in his first year, has done everything to intentionally divide America, not unite America. Leaders are uniters. Leaders are not dividers.

The issues today are so complicated and so interconnected because of the volatility of the world. If nothing else, that we have to get along, we have to work with each other. You can have strong opinions, of course, and fight mightily for what you believe. But in the end you’ve got to make government work. You have to compromise, you’ve got to sort it out. You can’t continue to vilify the other side and call them names and make so many comments that he’s made about his own intelligence agencies and people in the federal government and individuals. You can’t allow personalization to dominate your responsibilities as a leader.

You’ve got a president of the United States that continues to advocate this “America First” agenda with our allies in a world where we need friends, we need alliances. We’re not going to sort everything out by ourselves, certainly the military can’t fix problems alone. We need friends and alliances. We’ve built coalitions of common interest. When you start taking the United States out of treaties and trade relationships … that’s not the way to lead the world, to create vacuums and to continue to tell the world: “It’s America First, and I’m sorry about the rest of you.” America can’t lead that way, it’s not in our interest to do that.

Do you believe President Trump, through either his actions or his words, has made the world more dangerous?

Well, I don’t think he has helped address the volatility and the danger in the world by his words and by his leadership for the very reasons I just mentioned. American leaders, at least since World War II, have always attempted to reach out and to make friends to build new alliances, not divide alliances and impose tariffs on countries just arbitrarily, unilaterally. All these things have consequences.

You know, world affairs, geopolitics or domestic affairs, it’s like a mosaic. It isn’t normally just one piece that gives you the picture. It’s a number of pictures that come together in a mosaic, and then you start to see the clarity of what that situation is. Intelligence, economics, trade, politics, military, terrorism — all of that playing in, and a president of the United States must lead and not divide.

Was it wise for President Trump to remove the U.S. from the Trans-Pacific Partnership?

I think clearly we have been hurt by our walking away from TPP. Just the other day, the 11 other nations [from TPP] announced that they were going forward with a new trade organization, without the United States. China is everywhere. China lives there. China has influence in Asia-Pacific. Of course they’re filling that vacuum. Of course they are. The Russians are filling to some extent, too. The Indians will fill that vacuum. Of course it affects how we’re seeing our relationships. I hear from leaders in all those countries, leaders from all over the world, meet with ambassadors all the time, and they had the same story: “You are leaving a vacuum in these areas that the Chinese specifically are filling.“ Of course they will. It’s the story of mankind. It’s a story of history, it’s a story of great powers. And there will be no other way that this turns out.

You can’t rely just on your military as we have bases and facilities and assets all over Asia-Pacific. You can’t rely just on that to think you’re going to influence outcomes in the Asia-Pacific and you will continue to dominate. That ain’t the way it works. And so I think we are seeing our military put in a very difficult spot here. I think [it] is going to get worse and worse.

Do you think a pre-emptive strike on North Korea is an option?

If you want to bet that if you are going to attack North Korea, however you [are] going to do that, and think that Kim Jong Un and the North Koreans are not going to retaliate — it’s a pretty big gamble. I wouldn’t want to take that gamble. I know something about this business, and I know the kind of conventional capability North Korea has. I would ask this question: “What is winning?” There would be literally millions of people dead in South Korea, tens of thousands of Americans dead. We have 30,000 troops along the [Demilitarized Zone] plus other Americans there as well. Probably Japan doesn’t come out of this without some catastrophe.

If you’re willing to gamble that and say, “we can do this by just teaching a lesson,” that’s a pretty risky gamble. I wouldn’t do it. I don’t think you can do that. Let’s be smarter. Let’s find some ways to accommodate some kind of diplomatic settlement here, openings where we could find openings, and let’s cut the rhetoric, let’s cut the tension, let’s cut the nonsense and bravado, and let’s get busy and start following what the South Koreans are doing in finding openings with the North. Engagement is not surrender or appeasement. Great powers engage. Great powers talk to people. Great powers take responsibility. And that’s what we should be doing with North Korea.

Was it a mistake not to go into Syria with force and respond to the use of chemical weapons?

Well, we were ready to do it, as you know. It was a decision made by the National Security Council, a unanimous decision. I strongly favored it. At the last minute the president decided not to do it. I think it was a mistake, I’ve said that. We wouldn’t have had to kill volumes and volumes of people — there was a way to do some things to Assad’s government. And that was the intent. That was the strategy. So it is what it is. Would that event have changed the course of things in Syria? I don’t know.

But also I would say [that] at the time, the Russians were not there. I think it sent a very clear message to the Russians, very clear. When the Russians saw [us not attacking Assad], that action, that was clear to them that we were not going to be players in Syria and we were not going to be involved. And what they did is they took a little naval base, which was nothing, in Latakia province, and used that to build up a huge air asset campaign, troops on the ground, intelligence, navy. And now they’ve got a significant set of sophisticated assets in Syria and now really hold the cards in Syria.

What is the solution there? How does this shake out?

Well, I don’t think the United States is going to be anywhere near making that final decision. How could we? I mean, what capabilities, what leverage do we have? What card do we have? Two thousand people in northeastern Syria? To do what? The Russians are [there], and they’re not going anywhere, they’re in big time. Assad gets stronger every day. The Iranians are in there, they’re not going. The Turks now are opposed to us. So the question is: How is the United States going to influence the outcome of Syria? The Russians will. The Iranians, the Turks and Assad will, and of course remnants of ISIS are still there, [the] Nusra [Front], other smaller terrorist groups are still there. The freedom fighters are still.

But I don’t know where the strategy is or what they think there is going to be in this administration to be able to influence the outcome of Syria.

Turkey is going after Kurdish forces in Syria, some of whom were trained by the U.S. Is there a way to calm the situation?

We’ve got a problem with the Turks because we didn’t listen to them. I remember one of my last trips, last trip to Turkey, sitting down with Mr. [Recep Tayyip] Erdogen, [Turkey’s president], who I’ve known since 2002. He told me directly in fall 2014: “Mr. Secretary, ISIS is not our No. 1 threat. … The Kurds have been and will continue to be until we win. And we will do everything and anything we need to do to eliminate the Kurds.

Now, if a country says that that’s the No. 1 internal security interest, we’re not going to convince them otherwise. Now what do you do about it? Yes, we’ve got a NATO ally who has been an invaluable NATO ally since 1952 in Turkey. Do we want to walk away from that relationship? Because it has consequences. They’ll walk out of NATO. I don’t think that’s good for NATO, I don’t think that is good for the Middle East, I don’t think it is good for the United States. We work closely with the Kurds. How do we work through that?

Again, the only way to do this is some kind of a diplomatic effort to try to resolve as much as we can. But there’s a mistaken sense I think here in some quarters that the United States can fix every problem in the world.

Do you believe the U.S. will ever leave Afghanistan and Iraq?

I do. I mean, at some point we’re going to have to. After 17 years in Afghanistan the situation is worse than it’s ever been. I think the American people, the Congress, the United States are going to start asking some pretty good questions. It’s not because the American military failed, but the American military can’t fix the problems in Afghanistan. Poppy production, corruption, tribal decisions, topography. All the uncontrollables are there. You don’t fix that with the military. We tried that, had over 100,000 troops in there for a number of years. So yeah, we’re going to leave some point, sure.

Iraq. We will bring all those forces down. Iraq is a balancing act between Iran and the United States. Iran’s there. We’re not there. We don’t live there. The Iranians do. [The Iraqis] have a relationship with us, they want to keep it. So how long does that play out and what’s the objective? And all those things are going to be questions to be asked by the American people on the ground.