President-elect Donald Trump is nominating retired Marine Gen. John F. Kelly for secretary of homeland security. Here's what you need to know about him. (Sarah Parnass,Osman Malik/The Washington Post)

President-elect Donald Trump is nominating retired Marine Gen. John F. Kelly for secretary of homeland security. Here's what you need to know about him. (Sarah Parnass,Osman Malik/The Washington Post)

President-elect Donald Trump has selected retired Marine Gen. John F. Kelly as secretary of homeland security, officials familiar with the decision said Wednesday, recruiting a third former member of the military’s brass to serve at the highest levels of his administration.

Trump’s choice of Kelly — and his continued deliberations about tapping as many as two more military figures for other posts — has intensified worries among some members of Congress and national security experts that the new administration’s policies may be shaped disproportionately by military commanders.

“I’m concerned,” said Sen. Chris Murphy (D-Conn.), a member of the Foreign Relations Committee. “Each of these individuals may have great merit in their own right, but what we’ve learned over the past 15 years is that when we view problems in the world through a military lens, we make big mistakes.”

Despite making regular remarks on the campaign trail disparaging the nation’s generals, Trump has long shown an affinity for them. In shaping his administration, Trump has prioritized what one adviser described as “can-do, no-bull types,” which the president-elect sees as a deliberate contrast from the personnel choices President Obama has made.

If confirmed, Kelly and defense secretary nominee James Mattis, a retired Marine general with the nickname “Mad Dog,” would join retired Army Lt. Gen. Michael T. Flynn, Trump’s pick for White House national security adviser. Meanwhile, retired Army Gen. David H. Petraeus is under consideration for secretary of state, and Navy Adm. Michael S. Rogers is a contender for director of national intelligence.

President-elect Donald Trump has already tapped three former generals to serve in his administration. The Washington Post's Jenna Johnson explains what attracts Trump to these men. (Bastien Inzaurralde/The Washington Post)

Other figures with military backgrounds are populating the administration as well, including Rep. Mike Pompeo (R-Kan.), who graduated from West Point and served in the Army in the Gulf War, is Trump’s nominee to lead the Central Intelligence Agency, while Stephen K. Bannon, a former naval officer, will serve the president in the West Wing as chief strategist and senior counselor.

[What Trump may not know about the generals he’s eyeing for top positions]

Trump, who received multiple draft deferments and who has no military experience beyond his years at a military boarding school, is said to be drawn to generals by their swagger and dazzled by their tales from the battlefield.

Many of those he has been interviewing and consulting have spent much of the past decade and a half at war, intimately involved in the U.S. fight against global terrorism. Trump’s choices also are striking considering his noninterventionist posture in the campaign and sharp criticism of the war in Iraq and other military adventures.

As Trump formally introduced Mattis as his pick to run the Pentagon, he relished in recalling the general’s exploits, and he has likened him to George S. Patton, the legendary World War II Army general.

“ ‘Mad Dog’ plays no games, right?” Trump told a roaring crowd Tuesday night in Fayetteville, N.C. “Led the forces that went after the Taliban and commanded the First Marine Division in Iraq. He is one of the most effective generals that we’ve had in many, many decades.”

To be confirmed, Mattis would have to receive a waiver from Congress because the law requires the defense secretary be a civilian for at least seven years before taking office. Mattis retired in 2013.

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Sen. Patrick Leahy (D-Vt.) said of Trump, “For a guy who got four or five deferments from the draft, he seems pretty impressed with the military.”

Trump’s heavy reliance on military leaders marks a departure from the previous three presidents, who tapped a few generals for the highest jobs with mixed success and relied mostly on people who had spent decades in civilian service, as politicians or academics or lawyers.

“Trump is clearly operating out of a particular model,” said William A. Galston, a senior fellow at the Brookings Institution. “Almost all of his Cabinet will be made up of people from the military or people from a corporate background, and what they have in common is strong leadership and executive ­decision-making.”

Sen. Claire McCaskill (D-Mo.) quipped: “It’s the G&G cabinet. It does seem to be fairly limited to Goldman Sachs and generals.”

On Capitol Hill, the two generals Trump has nominated for Senate-confirmed positions — Mattis and Kelly — have been relatively well-received.

“Can you have a Cabinet full of generals? No — [not] any more than you can have a Cabinet full of lawyers or a Cabinet full of business people or whatever,” said Rep. Mac Thornberry ­(R-Tex.). But, he said: “I’m thinking of the individuals. They’re people I have incredible respect for.”

[Retired Marine general John F. Kelly picked to head Department of Homeland Security]

Kelly especially is likely to benefit from the relationships he cultivated among lawmakers during his years in uniform, including his role in 2014 as commander of the U.S. Southern Command, managing an influx of migrant children at the border with Mexico.

Sen. Thomas R. Carper (D-Del.), the former chairman of the Homeland Security panel, said Kelly has “genuine compassion” for immigrants and understands the root causes of the nation’s immigration challenges in such Central American countries as Honduras, Guatemala and El Salvador.

“I will reserve judgment on many of the president-elect’s other nominees,” Carper said, “but with General Kelly, he’s hit a home run with runners on base.”

There does not yet appear to be a Democratic strategy to derail either nomination because of the preponderance of military figures. Sen. Angus King (I-Maine), who caucuses with the Democrats, summed up the approach: “Take ’em one at a time.”

That posture could change if Trump nominates another general to a top post, such as Petraeus at the State Department.

Daniel Benjamin, the former senior counterterrorism official at the State Department in the Obama administration and now a professor at Dartmouth College, said having too many generals in what are traditionally civilian positions is “a matter of deep concern.”

“Generals as a rule believe in hierarchies and taking orders, and if the president gives them an order you have to wonder how likely they are to push back against it,” Benjamin said. “Generals have one set of skills, and diplomacy is not in the top drawer of that tool kit.”

On social media Wednesday, there was some snarky commentary about Trump’s emerging Cabinet resembling “a military junta.” Anthony Scaramucci, a Trump transition team official, defended Trump’s selections on Twitter: “Decorated American Generals aren’t warmongers — they’re among the most intelligent, disciplined & patriotic people our country has to offer!”

Most military officers have spent their entire careers within structured organizations with large staffs and clear chains of command. Sometimes they struggle in the more freewheeling world of politics and policy — to say nothing of what is expected to be the Trump White House’s unpredictable environment.

“Great generals don’t always make great Cabinet officials,” said Phil Carter, an Iraq War veteran and senior fellow with the Center for a New American Security.

Obama tapped as his first national security adviser retired Marine Gen. James L. Jones Jr., who had a highly successful military career but struggled with the politics of serving and was replaced relatively early in Obama’s first term. Similarly, retired Army Gen. Eric K. Shinseki served as Obama’s first secretary of veterans affairs, presiding over a bureaucracy that was overwhelmed by returning service members from Iraq and Afghanistan and scandals over forged records.

Other retired military officers had far smoother transitions to civilian administrations, including Brent Scowcroft, a former Air Force general who served as national security adviser to former president George H.W. Bush. Scowcroft is widely hailed as one of the most successful national security advisers in the history of the job.

“The United States military is the finest training organization in the world,” said Sen. Ron Johnson (R-Wis.), who will chair confirmation hearings for Kelly. “It produces real leaders, people who know how to solve problems and take a very structured approach to doing so.”

Galston, a Democrat who served as a White House policy adviser to former president Bill Clinton, said the concerns about generals “charging ahead” with no regard for legal or constitutional constraints — or without a willingness to challenge the president’s decisions — are misplaced. Galston said modern-day generals are trained to navigate a minefield of potential conflicts and legal concerns.

“They’re schooled to believe that if they or any subordinates receive an unlawful order, it’s not to be obeyed,” Galston said. “If you asked me, would I prefer a government of generals or a government of lawyers, that’s not an easy choice. We’ve experimented with a government of lawyers, and that hasn’t been so fantastic, has it? Maybe it’s time to give the generals a chance.”

Karoun Demirjian, Greg Jaffe and Greg Miller contributed to this report.