General Jim Mattis has served his country for his entire life. He is one of the most important and respected military leaders of the last half-century.

He also has the distinction of being the only person I know who has been fired by both Presidents Obama and Trump.

In both cases, it was to the administration’s — and the country’s — detriment.

However, in both cases, General Mattis also knew his duty was to the United States. That made him feel comfortable in disagreeing with his commander-in-chief.

I first knew General Mattis during the Iraq War under President George W. Bush, when Mattis was part of the Marine detachment in Kuwait. I was immediately impressed.

I later watched him continually adjust and adapt in the battle of Fallujah, which led him to a decisive victory.

His 44-year career as a Marine, which began when he enlisted in 1969 at age 18, has been stunning. He led Marine forces on the ground in some of the most dangerous places on the planet — including Iraq in 1991 and 2003 and Afghanistan in 2001.

His success eventually led him to become the commander of all Marine forces in the Middle East and later the commander of U.S. Joint Forces Command, NATO’s Supreme Allied Command for Transformation, and U.S. Central Command.

His non-combat service for the Department of Defense has been equally impressive.

I have greatly enjoyed and deeply appreciated working with him as he has served as U.S. secretary of defense.

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Few people alive today have embodied valor, courage, and sheer patriotism that matches General Jim Mattis.

One of my fondest memories with General Mattis was drinking wine and talking with him for a few hours after a meeting with then-Senate Armed Services Committee Chairman John McCain.

The respect for him at the Department of Defense is tremendous. The respect he has garnered around the world — from both our allies and enemies is breathtaking. Anyone who questions his patriotism or service is simply wrong.

When I told Mattis about my grandson’s fascination with Waterloo, he told me that he had never fully understood the conflict until he had read the Sharpe novel series by Bernard Cornwell about a British officer fighting in the Napoleonic Wars, which I passed on to my grandson.

I have come to know General Mattis as a remarkable intellectual — and perhaps the best-read officer the Marine Corps has ever produced.

The respect for him at the Department of Defense is tremendous. The respect he has garnered around the world — from both our allies and enemies is breathtaking.

Anyone who questions his patriotism or service is simply wrong.

Related: Trump Faces GOP Backlash Over Troop Reductions in Syria, Afghanistan

General Jim Mattis is an American patriot.

We should all be deeply thankful for the lifetime of service he has devoted to our country — and saddened that his service as secretary of defense has come to an end.

Newt Gingrich is a Fox News contributor. A Republican, he was speaker of the United States House of Representatives from 1995 to 1999. Follow him on Twitter @NewtGingrich. His latest book is “Trump’s America: The Truth About Our Nation’s Great Comeback.” This Fox News opinion piece is used by permission.

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