Secretary of Defense Ashton B. Carter and Chairman of the Joint Chiefs Gen. Joseph F. Dunford Jr. testify on operations against the Islamic State. (Jonathan Ernst/Reuters)

Dan Sullivan, a Republican, represents Alaska in the U.S. Senate and is a member of the Armed Services Committee. He is a lieutenant colonel in the U.S. Marine Corps Reserve.

When the president is in open disagreement with the secretary of defense and the chairman of the Joint Chiefs of Staff on one of the most critical issues our nation faces — whether to send our sons and daughters into combat — it should be cause for significant national concern.

President Obama has repeatedly told the American people that U.S. troops are not in combat in the Middle East. In 2010, he announced that “our combat mission is ending” in Iraq. He used the same words in 2014 regarding Afghanistan. More recently, he said that our mission in Syria “will not involve American combat troops fighting on foreign soil.”

Yet last week in a Senate Armed Services Committee hearing, I asked Defense Secretary Ashton B. Carter and Joint Chiefs Chairman Gen. Joseph F. Dunford Jr. if our troops in the Middle East, including in Syria, are engaged in combat. Both unequivocally said yes. To our members of the military serving overseas, Carter and Dunford were stating the obvious.

Indeed, recent reports in The Post and the Military Times describe up to 200 Marines at Fire Base Bell in northern Iraq firing artillery daily in support of Iraqi troops and killing Islamic State terrorists. Our soldiers serving as part of the Joint Special Operations Command in the Middle East conduct regular counterterrorism missions to kill and capture terrorists. Since 2014, our brave pilots have dropped approximately 40,000 bombs in Iraq and Syria in close-air-support missions focused on killing Islamic State members and destroying their infrastructure and supply operations. An additional 1,200 bombs have been dropped supporting the coalition fight in Afghanistan combating the Taliban.

Some of our service members have been killed conducting these operations, while others have been wounded. All of this is the very definition of combat.

To Carter’s credit, he said at the hearing: “These people are in combat . . . and I think that we need to say that clearly.”

Apparently, the White House didn’t get the memo. This week, when asked about a Navy SEAL killed in a fierce firefight involving U.S. Special Operations forces, Kurdish commandos and Islamic State fighters, White House spokesman Josh Earnest told reporters that “the relatively small number of U.S. service members that are involved in these operations are not in combat but are in a dangerous place.”

Why do Obama and his White House continue to peddle the fiction that U.S. forces are not engaged in combat? Perhaps the commander in chief is truly unaware that they are, which would be troubling indeed. More likely is that because he’s told the American people repeatedly that he will end wars and won’t send combat troops to the Middle East, the word contortions coming from the White House are part of a twisted attempt to salvage and protect the president’s legacy.

But by spinning the truth for political purposes, the president is coming perilously close to leaving a legacy of dishonesty when it comes to our military involvement in the Middle East. And much more worrisome, such dishonesty comes with costs.

First, it diminishes the service and sacrifice of our troops and their families. Americans serving in Iraq, Syria and Afghanistan know they’re engaged in combat operations. The commander in chief needs to acknowledge this fact and the bravery it entails, not disguise the true nature of their duty.

Second, it further undermines the administration’s tenuous foreign policy credibility regarding its stated goal of degrading and destroying the Islamic State. While this is the correct goal, a series of missteps in the Middle East, including the president’s failure to enforce his own red line when it was crossed by Bashar al-Assad in Syria, have brought us to the point where our adversaries and our allies question U.S. credibility and resolve. Islamic State terrorists know that they’re in combat against U.S. forces, but when the president says otherwise, it signals a lack of conviction, making it harder to defeat these terrorists.

Finally, the dishonesty about the role of our troops allows our presidential candidates to duck a tough issue. Hillary Clinton repeatedly has been allowed to say, unchallenged, that she would continue the president’s policies of not sending combat troops to Syria and Iraq.

Forty-five years ago, future Secretary of State John F. Kerry, then speaking as a veteran of the Vietnam War, urged the incumbent administration to be honest about the roles our men and women in uniform were playing in Vietnam. Testifying before the Senate Foreign Relations Committee, he said, “We veterans can only look on with amazement on the fact that this country has been unable to see there is absolutely no difference between ground troops and a helicopter crew, and yet people have accepted a differentiation fed them by the administration.”

The theater has changed, but Kerry’s words still resonate. For the betterment of our troops, and our country, he called for honesty then — just as we all should call for honesty now.