Even as the White House legal counsel briefed Democratic senators on President Barack Obama’s draft for new war powers against the Islamic State last week, Sen. Bob Corker, chairman of the committee charged with authorizing war, was hesitant to reveal its details to a reporter. He had given the White House his word he would keep the president’s proposal confidential until the authorization for the use of military force, or AUMF, was sent over to Congress formally.

“They’ve trusted me with that material,” the Tennessee Republican explained. He later wrapped his interview with Defense One with an apology, saying he was late to a call with the White House.

This is Corker – a careful and thoughtful counterweight to the jump-to-action style of the more hawkish members of his party. You won’t often see him on the Sunday shows, but quietly, behind closed doors, he’s the GOP senator with a direct line to the president.

The soft-spoken businessman who was once seen as too moderate and independent is now one of the most important figures in Washington for the war against the Islamic State as chairman of the Senate Foreign Relations Committee. From this perch, Corker will preside over the first full debate on war powers and U.S. military intervention in more than a decade. It’s a policy fight that could shape U.S. national security strategy beyond Obama’s last two years in office, for years to come.

While Corker rejects the “moderate” label, he’ll gladly take pragmatist. “I don’t view myself as a moderate in any way,” Corker told Defense One. “I do view myself as someone who tries to solve problems. In a body where votes matter, you have to have a majority, and certainly bringing the two parties together is important, especially on big issues.”

He believes he’s uniquely suited for the job, though he never anticipated he’d be at the center of the next chapter of the global war on terror. “Before I came into the Senate [in 2006], I built shopping centers around the country, right? I owned and operated commercial real estate, I’d been the mayor of a city,” he said. “I came on the Foreign Relations Committee really, you know, to sort of broaden my understanding of the world and become a better senator. I’ve been to 63 countries now.”

I don’t view myself as a moderate in any way. I do view myself as someone who tries to solve problems. Sen. Bob Corker, R-Tenn.

In spring of 2011, Sen. Chris Coons, D-Del., travelled with Corker to Afghanistan. It was Coons’ first trip. They arrived to a briefing from U.S. agencies on the single largest theft of U.S. government funds in history, nearly $1 billion, and allegations it had been facilitated in part by the extended family of Hamid Karzai, then president of Afghanistan. They met with Karzai that same day.

“Sen. Corker, as a result of being very upset, said a number of things to Karzai that were exceptionally direct and blunt, and Karzai, without batting an eye, responded in kind,” described Coons, who also serves on the Foreign Relations Committee. “It was a truly memorable exchange. And as a newly-minted senator, I was looking at the security guards in the room, thinking, ‘Are we going to make it out of here?’”

In his office in Washington, Corker describes it a bit differently. “We work over-time to make sure that we don’t just know the situation from reading about it, but we’re there on the ground, seeing what’s happening, meeting the leaders, understanding the different currents, trying to figure out a way to move ahead in a way that will be successful for U.S. national interests,” he said.

Corker will kick off the new AUMF debate with hearings in his committee after Congress returns from recess this week.

“It is one of the most important votes, if not the most important vote, a senator will ever make,” Corker said.

(Related: Obama’s ISIS War Powers Request Has Few Limits on Who, Where, How)

But the heated disagreement over the AUMF is already becoming a high-profile platform for the larger ideological fight that is looming over the fundamental question: What should be America’s role in the world? Corker politely declined to put himself on a spectrum of the widely divergent views within his own party, ranging from Arizona Sen. John McCain’s muscular view of American foreign policy to the less-interventionist views of Kentucky Sen. Rand Paul.

“I approach things in a very pragmatic, realistic way,” Corker said. “I do absolutely embrace the concept of American exceptionalism, at the same time I realize there are limits to what we can successfully carry out.”

Especially as the U.S. political machine ramps up for the 2016 elections, Corker said, it’s easy to try and squeeze the current, ever-morphing security climate into a neat ideological tagline. But the unexpected spate of foreign policy crises has disproven many such pronouncements.

“If you think about it, under [President George H.W.] Bush 41, and under [President Ronald] Reagan, you have this sort of bipolar situation -- you have the Cold War, it’s basically us and the Soviet Union. That all dissipated back in 1991,” he said. “Then you had [President George W.] Bush 43 who came along, and you had nothing but sort of asymmetric warfare -- it was all about terrorism. And now you look at where we are today in 2015, and you’ve got a combination of the two,” he said, using Ukraine and the Islamic State fight as examples.

“Here we are again with Russia, you know, totally destroying if you will the 70-year policy that we’ve had that Europe would be whole, Democratic and free,” he said. “We have great concerns here about that fact that, here Ukraine is, it basically wanted to move West -- we cheered them on. We pulled them our way. And here in their time of need, when they have a Russia that’s pouring arms in, pouring troops in, and you know, here we’re not even willing to give them defensive armaments?”

I do absolutely embrace the concept of American exceptionalism, at the same time I realize there are limits to what we can successfully carry out. Sen. Bob Corker, R-Tenn.

At the same time, he said, “We’re dealing with ISIS, in a situation where there’s no longer a two-country issue. There are eight countries today in asymmetric type warfare, except that we have for the first time a terrorist group that’s able to occupy and hold territory.”

Then there’s China, Iran and the rest of the world. “Now you tell me what a few sentences about foreign policy for all of that would be,” Corker finished.

Beyond divisions among lawmakers over many elements of the White House proposal for the AUMF, Corker said the most challenging issue may be a question of Obama’s resolve for the Islamic State fight, and making sure that “it’s not something where we’re halfway into it just to appear to be making effort.”

“I think one of the bigger issues for people is really getting a sense from the administration that they are committed to something that is successful ... I’m already getting that,” he said. The White House strategy thus far is, he said, “something that feels like it’s more superficial than substantive.” Corker argued that’s why it was important for the White House to first draft and send Congress an AUMF. Now they must sell it.

“The stated mission is to degrade and destroy,” he said. “But I do think in Syria in particular there’s a much bigger emphasis on degrade -- another word that’s been used is containment.” But is that dangerous? “I’m concerned that here we are training free Syrian opposition and yet they’re being barrel bombed by [Syrian President Bashar] Assad. We’re actually losing them more quickly than we’re gaining population, and to me that’s a problem that’s a significant problem. So how do you counter that?”

(Related: Even Containment Needs Boots on the Ground)

In Iraq, Corker said, “We have more going for us.” But the president’s “Iraq-first” strategy won’t be easy, either, he said. “You have the complexities of a Shia militia going in and dealing with large Sunni populations, that’s not probably gonna be perceived particularly well.”

Corker argues that had the U.S. provided real support for the Free Syrian Army at the beginning of the civil war three years ago, and had Congress approved a plan for limited air strikes against the Assad regime in September 2013, it would’ve degraded Assad’s forces and given momentum to the opposition that could’ve helped close the vacuum the Islamic State and other militant groups have since filled.

He said it’s difficult to see how elements of the administration’s strategy against the Islamic State in Syria can succeed – that, effectively, the White House has no Syria policy. It’s one of the mainstream Republican talking points lately levied against the president, and Obama’s national security and military leaders repeatedly are made to reiterate the outline of the strategy to defeat ISIS. Corker, like many Republicans, also blames the Obama administration for withdrawing all U.S. troops from Iraq in 2011, but he includes former Iraqi Prime Minister Nouri al-Maliki in the responsibility.

But even in that criticism, Corker wouldn’t take a parting partisan shot.

“Now that’s past, ok,” he said. “We gotta deal with present.”