Trump's Defence Secretary James Mattis makes passionate case against America withdrawing from the world

James Mattis, one of the key members of Donald Trump's “America first” administration, has launched a passionate defence of the United States as an internationalist power.

The Defence Secretary was speaking at a troop event in Washington when he was asked by a young naval officer whether the US should “get back to our isolationist roots” in the face of a complex global economy and “instantaneous information”.

Mr Trump's nationalist platform propelled him to victory in last year's election, under the slogan “Make American Great Again”. He said the US had been “very badly treated” in trade deals with a number of countries including Germany and China, a theme he has continued to pursue in office by withdrawing from the Trans-Pacific Partnership.

He has also been critical of Nato, the defence alliance in which the US plays a pivotal role due to its overwhelming military might, once calling it “obsolete”, though he subsequently endorsed the group. In July Mr Trump also announced the US would pull out of the Paris climate agreement, despite being a major polluter.

Mr Mattis, a 66-year-old former Marine Corps general, told the officer at Kitsap naval base on Wednesday: “If we were standing here in 1945, let's say, December. It's Christmastime. You guys are coming back in from all over, places called Japan, Okinawa, Iwo Jima, Philippines. You've taken the Army and the Marines all over.

“Now, you've grown up in a depression, when your dad didn't have a job and he couldn't find work no matter what.

“You've just gone through a war that cost us hundreds of thousands killed and wounded. We're not sure how many millions—40 million—people dead.

“And they looked around, and they said, what a crummy world. And they said, like it or not, we're a part of that world, and they did something. They made the United Nations. It's still not perfect; a lot better than nothing. They made Nato.

“They could have said, ‘We're through with you, we're going to work with Latin America and … the Middle East. We're just not going to put up with any more of your crap.’”

“Instead, we put in Nato, sent US troops over, and we said 100 million Americans may die in a nuclear war, but we're going to stand with you Nato, all of Europe, Western Europe. You're not going to fall to the Soviets.

“We put together something called the International Monetary Fund, so people for economic reasons wouldn't be driven to elect a guy like Hitler—you what I mean?—as the answer.

“And by the time they got done, they created a new world order.

“So, do we return to our isolationist roots? We could only do that if we forget the example, forget the example ... of the Greatest Generation. And we ought not [to] forget that example. They're not called the Greatest Generation for no reason, OK?”

However, Mr Mattis warned earlier this year that the US may ”moderate its commitment“ to Nato if other member countries did not pay their way.

Mr Trump has frequently criticised nations that do not spend the requisite portion of their GDP on defence.

Mr Mattis said, during closed-door talks in Brussels in February: “I owe it to you to give you clarity on the political reality in the United States, and to state the fair demand from my country's people in concrete terms.

“America will meet its responsibilities, but if your nations do not want to see America moderate its commitment to this alliance, each of your capitals needs to show support for our common defence.”