Secretary James “Mad Dog” Mattis doesn’t mind taking a moment to share his thoughts about the importance of diplomacy and development, as one intrepid high school student discovered.

Teddy Fischer, a sophomore at Mercer Island High School in Washington State, noticed Secretary Mattis’ private cell phone number in a Washington Post photo (since removed from the article). Fischer, a staff writer at his school paper The Islander, gave the retired general a call and left a message.

And Secretary Mattis called him back.

They set up an interview, and as it turns out, the two took the opportunity to talk about the three D’s: American diplomacy, development and defense. Here are the top highlights from Fischer’s interview with the 26^th Secretary of Defense.

The relationship of the Departments of State and Defense: “What you have to do is make certain that your foreign policy is led by the diplomats, not by the military,” said Mattis. “I meet for breakfast once a week with Secretary of State Tillerson and I’ll advise him on the military factors for his foreign policy, but I do not believe that military issues should lead in foreign policy. I think that’s where diplomats lead and the military then reinforces the diplomats.”

U.S. leadership in a post-ISIS Middle East: “You don’t have to have the Americans do it all,” said the Secretary of post-conflict development, noting that U.S. leadership inspires support from other nations. “The Americans can lead it in terms of organization because many nations don’t trust each other as much as they trust America,” but it’s “going to be an international effort,” much like the Marshall Plan after World War II, when the U.S. and allies helped rebuild war-torn nations. And the results? “Look at us today… Germany and Japan are two of our strongest allies.”

Isolationism and lessons from history: “We can’t just be isolationist like we were after World War I.” Out of “the great World War II generation” came the outlook behind the creation of the Marshall Plan, “that, like it or not, we’re part of a world.”

Defeating extremism through global development: Ideologies aren’t fought primarily by the military, but by investing in programs that open up educational exchanges and economic opportunities. “I think ideologies can be countered by showing people a better education and hope for the future by learning how to get along with one another. And for all of our problems in our country, we’re probably still the best example of that in the world.”

The proposed budget cuts to USAID and the Millennium Challenge Corporation: “As Winston Churchill put it, once the American people exhaust all the alternatives, they’ll do the right thing. I think we’ll see the right thing done” in preserving funding for the two development agencies.

Youth empowerment and education: Helping expand country-led educational opportunities for young people is “the most enduring way” to improve societies, specifically in the Middle East. “By having everybody feel like they’ve got a sense of the future and a stake in the future, especially the young people, you can create a positive environment economically, politically, and diplomatically,” which ultimately helps stabilize nations.

Preventing war through diplomacy: “Do everything you can not to go to war if at all possible,” said Mattis. The way we prevent that is through civilian political leadership, “because in our society, those decisions are made by civilians, and not by the military.”

And why did Mattis return Fischer’s call? “I’ve always tried to help students because I think we owe it to you young folks to pass on what we learned going down the road so that you can make your own mistakes, not the same ones we made.”

Check out the full interview transcript here.

Image: DOD / U.S. Air Force Tech. Sgt. Brigitte N. Brantley / U.S. government use