Since World War II, the United States has provided global leadership to promote peace and prosperity. Doing so was the best way to strengthen and protect both our values and our national security interests. Every president since Franklin Roosevelt recognized that the blood spilled in the fight against fascism and communism would light the torch of a foreign policy committed to the principles of our democracy – and that torch would be passed on to future generations.

The preamble of our Constitution defined those principles – a more perfect union, justice, domestic tranquility, a common defense, the general welfare and the blessings of liberty for ourselves and our posterity. These are the values that every generation of Americans has embraced as fundamental to the American dream – values for which our men and women in uniform have been willing to fight and die to protect America.

In keeping with those values, America has been a leader in the world community – in establishing the United Nations, in fighting the Cold War, in creating the North Atlantic Treaty Organization, in negotiating nuclear nonproliferation agreements, other trade and arms control treaties and the international Paris accord on climate change. The world is a better and safer place because of our leadership.

Is that era of American leadership now coming to an end? President Donald Trump deliberately ignores the lessons of history; insults our closest political, economic and moral allies; backs away from international agreements and responsibilities; and praises strongmen and dictators who oppose our values. Is the United States policy of fighting for peace, human rights and justice for all to be replaced by a policy of selfishness as the primary driver of foreign policy?

Announcing last week that the U.S. would withdraw from the Paris accord, the president made clear that the morality of protecting our planet and our children from climate change has nothing to do with anything. The values of sacrificing for a better life for our children has been replaced by the principle that everything is about self-interest. Is this narrow and greedy approach to leadership in the 21st century to become the hallmark of America's foreign policy? I don't think so.

I believe in the resilience of American leadership. Our nation has faced crisis throughout our history, from wars to depressions to natural disasters. We have always risen to the occasion, and I believe we will again. Why? Because the real strength of our nation does not reside solely in Washington but in the spirit of the American people. As secretary of defense, I have seen it in the eyes of our men and women in uniform, who are willing to put their lives on the line to protect America. For them, it is about our values. During the debate on the constitutional amendment to prohibit flag burning, former Pennsylvania Democratic Rep. Jack Murtha, a decorated Marine who fought in Vietnam, said on the floor of the House that he opposed the amendment because he and others fought to protect the right of all citizens to freely express their views. That loyalty to our principles goes to the heart and soul of what our democracy is all about.