Chuck Hagel, who spent more than a decade in the Senate asking witnesses questions at hearings, will be the one answering them Thursday as his confirmation hearing to be secretary of defense begins.
His hearing follows that of Sen. John Kerry, D-Mass., who was confirmed this week to be secretary of state.
Kerry and Hagel have a prominent biographical detail in common: service in Vietnam.
"As a veteran of war, I will always carry the consequences of our decisions in my mind," Kerry said at the start of his confirmation hearing.
And when President Obama announced his choice of Hagel for defense secretary, he said: "To this day, Chuck bears the scars and the shrapnel from battles he fought in our name."
The White House emphasizes that both Kerry and Hagel understand the full cost of war in money and in lives. Obama says he believes that makes them the right men for this moment, as the administration shifts its approach following a decade of big, expensive, bloody wars in Iraq and Afghanistan.
As Tommy Vietor, a White House spokesman, puts it: "I don't think we can necessarily say without a doubt that there will never be a large war again. However, certainly we've moved conceptually toward a more targeted, surgical approach that focuses on al-Qaida.
"So you don't have this 100,000-troop footprint in Iraq to deal with a far smaller group of individuals that are actually targeting the United States."
The "targeted, surgical approach" that Vietor describes relies less on the military and more on the CIA which brings up Obama's third major national security nomination: CIA Director-in-waiting John Brennan, a longtime Obama adviser.
"Al-Qaida seeks to bleed us financially by drawing us into long, costly wars that also inflame anti-American sentiment," Brennan said two years ago during a speech in Washington. "Our best offense won't always be deploying large armies abroad, but rather delivering targeted, surgical pressure to the groups that threaten us."
There's that phrase again: "targeted, surgical." When Vietor is asked if that's a euphemism for drones and a kill list, he says: "The way we think about this for a president is, he doesn't have a choice about whether to do counterterrorism operations or not. There are threats to the United States, and his obligation is to protect the American people.
"He has a choice about how he conducts these counterterrorism operations."
So these three nominations Kerry, Hagel and Brennan represent a shift in the way the U.S. wages war. It's a shift from big to small, from the Pentagon to the CIA.
Legal experts say it's also a shift from clear, public rules to murky, secret ones.
The rules for invading a country are well-established and were developed over hundreds of years. But when the U.S. decides to go after a small group of suspected terrorists spread out in many different countries, it's a whole new ballgame, says Benjamin Wittes, a senior fellow at the Brookings Institution.
"That is a much, much more complicated and much less charted area of international law, of U.S. domestic law, in some ways," he says. "It's an area that is really important to the future, as represented by these nominations, I think."
It's controversial, too. Obama has had some pushback, though more overseas than at home. Regardless, it's now part of his legacy, says Karen Greenberg, who runs the national security program at Fordham University's law school.
"Remember, President Obama accepted the Nobel Peace Prize by saying war is necessary," she says. "He's somebody who understands, to his mind, what he sees as the need of war to create peace."
Former Ambassador Robert Blackwill, who held national security positions in the Bush administration, says he thinks this is a step that any president would have taken.
"We've been at war for the longest period in American history," Blackwill says. "We're, as a country, exhausted by these long wars we've been fighting, and I think that's the broad view of the American people now."
He says any president is a politician, answerable to the will of the American people and right now, the American people want restraint.