ABOARD A MILITARY AIRCRAFT — Acting Defense Secretary Pat Shanahan had a rocky meeting with U.S. senators at a security conference in Munich, Germany, over the administration’s plans on Syria, that could affect his chances to become President Trump’s permanent defense secretary.

At one point during the meeting, Sen. Lindsey Graham (R-SC), who was leading a delegation of U.S. senators and lawmakers to the security conference, told him, “That’s the dumbest f-cking idea I’ve ever heard,” according to several who were in the room.

Another senator allegedly told him, “You just lost the Senate.”

The meeting happened inside the Bayerischer Hof Hotel, a luxurious five-star hotel where world leaders and officials gathered for the three-day annual conference to discuss world affairs and hold official meetings on the sidelines. More than 50 members of Congress attended, as part of several delegations from the House and Senate.

The meeting with Shanahan took place Saturday morning at the hotel in a meeting room with more than a dozen members of Congress, both from the House and Senate, Republicans and Democrats.

Graham and other members of Congress recounted details of the meeting to journalists from Breitbart and the Washington Post, as they flew home from Munich aboard a military aircraft.

The exchange was centered on the Trump administration plan to withdraw all U.S. troops from Syria by April 30.

Graham’s goal at the conference was to convince key military allies to leave a couple hundred troops in Syria each, to prevent the reemergence of the Islamic State in Iraq and Syria. If successful, Graham would report back to Trump and possibly get him to do the same.

“So I came in and sat down, and said I’m sorry I’m late, but I got a question, ‘Are you telling all of our allies that we’re going to go to zero [troops in Syria] by April 30th?” Graham recalled.

“Yes, that’s been our direction,” Shanahan said, according to Graham. “And I said, ‘That’s the dumbest f-cking idea I’ve ever heard.’”

Graham said he asked Shanahan whether he agreed that if all 2,700 U.S. troops were pulled out of Syria, that ISIS would come back, Turkey and the Kurds in Syria would start a war, and Iran would gain more power in Syria.

“He said, ‘That could very well happen.’ [I asked] ‘Do you agree with me that if a couple hundred of us were committed to this buffer zone it would change everything?’ And he said, ‘Yes.’”

Graham said he told him, “‘Well, if the policy is going to be we’re leaving April 30, I am now your enemy not your friend … I’ll be your adversary. I’ve been busting my ass going all over the world trying to get Turkey to make this happen.’”

Shanahan then asked him, “Well what do you want me to tell people about you being an adversary?” Graham responded to Shanahan, “That you own it.”

At that point, another senator allegedly told Shanahan, “You just lost the Senate.”

Graham said there was a moment when all members present chimed in with support of the plan.

“‘For 200 people you could pull this off, may have the best chance I know of pulling it off,’ and that’s when everyone jumped in basically unrestricted — ‘Yea!’ And it was overwhelming — [Democrat Rep. Tom Malinowski (NJ)] — everybody…it was a real moment,” he said.

Several sources at the meeting said Shanahan “sat there like a deer in headlights,” in addition to other unflattering characterizations.

Sen. Sheldon Whitehouse (D-RI), the top Democrat on Graham’s delegation, added, “I’ll just say he did not have a very good meeting,” he said.

But Graham did express some sympathy for Shanahan on the withdrawal plan. “He’s just telling us what the plan is,” he said. But, he said, the meeting was the “defining moment of the trip.”

The Pentagon disputed that the meeting went badly. “They had a very constructive and positive meeting, and beyond that we just don’t comment on his private conversations,” said Acting Pentagon Press Secretary Charlie Summers.

Another government official also disputed that it went badly. The official said the meeting covered a range of topics, that Shanahan presented the Defense Department’s position on Syria and informed senators that it is generating options, and that the meeting ended on a positive note.

The official said that in fact, Shanahan generated agreement on the issue of China. Another source said Graham seemed satisfied by the end of the meeting.

However, more clashes on Syria are likely to come between Shanahan and Congress, as the military drawdown continues.

Graham said leaving a small stabilization force in northern Syria would prevent ISIS’s comeback, prevent a new war between two U.S. allies who are bitter enemies — Turkey and Kurdish forces, and to prevent Iran from gaining a deeper toehold there.

The stabilization force would consist of 1,500 forces, including 200 U.S. forces on the ground. Graham has also been arguing for leaving a small U.S. force at al-Tanf, a small military base in eastern Syria, to prevent Iranian proxy forces from establishing a presence there, and creating a long-desired corridor from Tehran to Beirut.

Graham, who has become a close ally of Trump, said he has discussed the idea with the president, who has indicated he would be receptive to leaving 200 U.S. troops there if allies committed forces, too.

“The Trump way is some of us, most of them, they do the fighting. That is a narrative that shows he’s a capable commander in chief that can get results that eluded others,” he said.

However, Graham said allies would not commit unless the U.S. did first. Thus, Graham and others viewed Shanahan’s message to allies that the U.S. would go down to zero troops by the April 30 deadline as counterproductive.

Lawmakers said there was broad — if not unanimous — bipartisan support from members of Congress present at the meeting for Graham’s plan.

They also said the U.S. commander of NATO forces and European Command Army Gen. Curtis Scaparrotti also expressed support, as did U.S. envoy to Syria Amb. Jim Jeffrey. Graham said that, despite the testy exchange, Shanahan did ultimately express support for the plan.

Shanahan said little about the meeting with reporters afterwards, mostly commenting on his meetings with allies:

What I was told is that this was a very productive one in that the type of dialogue and discourse was very frank and I have to say it felt like we were making progress on plans going forward on Syria. … So to me that was a very, very valuable time spent there. Then just a whole host of interactions with Congressional members, a number of bilateral and now it’s on this trip home, kind of wrapped together all the action items so that on Sunday I can do my laundry, head into work and kind of start working down the list. Good trip I think.

The trip to Munich was Shanahan’s first time attending the security conference as acting defense secretary and was seen as part of his “debut” on the world stage. He arrived in Munich on Friday after a trip to Afghanistan, Iraq, and a NATO defense ministerial in Brussels, which went off without a hitch.

While Shanahan has never said he wants the defense secretary job permanently, his performance as acting defense secretary is widely seen as an audition for the role, and so far, Trump has said positive things about him.

A senior White House official told Breitbart News on Tuesday: “Acting Sec Def Shanahan is widely liked in the White House.”

Shanahan can serve as acting defense secretary for an indeterminate time, according to laws governing the Pentagon, but if he were nominated for the position permanently, he would have to be confirmed by the Senate.

Before being tapped by Trump as acting defense secretary in December, Shanahan had served for 17 months as James Mattis’s deputy. Prior to that, he worked in the defense industry at Boeing for more than three decades and developed a reputation as a “fix it guy.”

Shanahan, however, has faced comparisons to Mattis, who was revered around the globe as a tough general and experienced statesman. Before Shanahan left for the trip, Senate Armed Services Committee Chairman Jim Inhofe (R-OK) told reporters that Shanahan was not as “humble” as Mattis.

Inhofe later clarified that he was joking, and made it a priority to see Shanahan in Munich, after he arrived separately from Graham’s delegation. He told a Breitbart News and a Defense News reporter that he liked Shanahan.

“We’ve known each other for a long time. I’d be happy to have him as a secretary of defense and could work with him very well. And I think we’ve accomplished that,” Inhofe said after his meeting with Shanahan. Inhofe later tweeted a picture of himself and Shanahan at the conference.

Whitehouse also acknowledged that “following Mattis was a hell of a job,” but said he did not know Shanahan well enough to have an opinion about whether he was qualified for defense secretary.

Inhofe said he had liked former Arizona Sen. Jon Kyl (R) and Air Force Secretary Heather Wilson, but said they had been “eliminated.”

Graham has personally endorsed retired Vice Chief of Staff of the Army Gen. Jack Keane, who helped architect the successful surge in Iraq during the George W. Bush administration that turned the tide in the war.

A former senior administration official cautioned against judging a defense secretary based on one issue.

“So the question is, what does the secretary of defense have to do? The secretary of defense is responsible for making sure our men and women in uniform and our civilians … have the capabilities they need to do their job across the world,” the former official said.

“You have to be able to lead a bureaucracy that is very complicated, that has many aspects to it, whether you’re talking about cyber, or the development of advanced weapons, whether you’re talking about personnel policies. Shanahan brings a lot to the table having led complex organizations and from the time that he spent as deputy.”