As for the Pentagon’s view on the Iraq invasion at the time, Mattis said this: “I think people were pretty much aware that the U.S. military didn’t think it was a very wise idea. But we give a cheery ‘Aye aye, sir.’ Because when you elect someone commander in chief — we give our advice. We generally give it in private.”

Mattis was one of the Iraq campaign’s most important ground commanders. He led the 1st Marine Division during the invasion and later oversaw the bloody retaking of Fallujah from insurgents in 2004.

Mattis was not among the six retired generals who went on the record in 2007 to criticize Donald Rumsfeld’s management of the war. Trump himself has criticized the Iraq invasion, and falsely claimed that he spoke out against it from the beginning. His choice for national security adviser, Gen. Michael Flynn, told Der Spiegel that the invasion was a “huge error” and “strategic failure.” Elsewhere, Mattis has called the Iraq and Afghanistan wars “poorly explained and inconclusive.” But if Mattis was among those who did not agree with President George W. Bush’s decision to invade, he did a good job of hiding his personal views. His famously gung-ho message to U.S. Marines on the eve of the invasion urged them to “fight with a happy heart and strong spirit” to unseat a dictator who “murdered the Iraqi people … and threatened the world with weapons of mass destruction.”

Mattis, who has recently been described as “outspoken” and “direct,” has openly criticized the Obama White House for not taking a harder line on Iran. But more than 10 years on, Mattis is yet to publicly question President George W. Bush’s decision to start the war, in which more than 1,000 U.S. Marines have died, despite the fact that the “weapons of mass destruction” were never found.

On the audio recording from the conference, Mattis can be heard worrying aloud about how far his views on Iraq will spread. “Dave, is this being — going out to the media?” he asks. “It could be recorded, but is that for internal …” Peggy O’Connor, a spokesperson for ASIS, said the luncheon was open to exhibitors as well as anyone else who bought a ticket. “There were several thousand people in the room,” she said, though she was not aware of any media.

The contrast between Mattis’s discrete treatment of one administration’s military approach to the Middle East and the next administration’s more diplomatic approach is striking. Some of the contrast is likely a function of seniority. Before he was reportedly fired in 2013, Mattis served Obama as head of U.S. Central Command, a role in which he would have had more input into policy than he did as a one-star general under Bush 10 years before. But Mattis’s deference to the president’s constitutional war-making powers raises the question of whether Congress should make an exception to a law that prohibits retired officers who, like Mattis, have been out of uniform for fewer than seven years, from serving as secretary of defense, a civilian office. If Trump, like Bush, attempted to start an unprovoked war of aggression, would Secretary Mattis be a stabilizing voice? Or would he say “aye aye, sir”?

“Nobody elected me,” Mattis told the audience in 2015. “But I did feel I had to be heard. And I was very blunt. And I gave my advice. But when it’s all over and done with, ladies and gentlemen, your military is obedient to the Constitution that says we obey the president. We swear an oath to protect that Constitution, and we live up to it. Loyalty only counts, we say, when there’s one hundred reasons not to be.”

Retired Marine Col. Mark Cancian, a senior adviser at the Center for Strategic and International Studies, said that Mattis’s remarks on the Iraq invasion demonstrated “a willingness to accept a hard ‘lesson learned.’ Many Republicans and military are still not willing to say that.”

In addition to comments on Iraq and the military’s role in decision-making, the speech contains some of Mattis’s most candid remarks to date on Iran. Mattis said that he read the 156-page Iran nuclear agreement twice. “It’s probably as good a document as we could have come out with,” he said, “even though it’s not one that I would have wanted to sign.” The Obama administration, Mattis said, lost its leverage with Iran after failing to follow through on a threat to use force against Syrian President Bashar al-Assad for crossing an explicit “red line” prohibition on the use of chemical weapons. During the Iran negotiations, Mattis argued, “the military option was not a believable one.” Elsewhere, Mattis has suggested that there is some link between ISIS and Iran.

The recording of Mattis’s speech was provided to The Intercept by Jakob S. Boeskov, an artist in New York who attended the ASIS 2015 event as part of an art project called “Face Jagger” and paid $5,200 for a booth and an exhibitor pass, which allowed him to display what he describes as “a fictitious cyber weapon.”

“Deception has been part of military strategy since the dawn of man,” Boeskov wrote in a statement accompanying the release. “But truth is needed in the civilian parts of society. The Iraq War was based on misinformation and fabricated stories about weapons of mass destruction. All rules change when politicians lie. Not only for art but also for military leaders. When politicians lie, a military leader has the right to say no to war.”

The Trump transition team was provided with a copy of the recording late Sunday. When reached on Monday morning, a transition spokesperson did not dispute the authenticity of the recording, nor did he offer any comment.