To prepare for his Afghanistan decision and Nobel address, President Obama visited Dover Air Force Base in Delaware in 2009 to witness the return of 18 Americans killed in Afghanistan, including Sgt. Dale R. Griffin of Terre Haute, Ind. (Saul Loeb/AFP/Getty Images)

Air Force One, its windows blacked out to guard against attack, touched down in Afghanistan well after dark.

President Obama’s war-zone visits are usually short and ceremonial. In his six hours on the ground, he appeared alongside Afghanistan’s leader, pinned Purple Hearts on the wounded and spoke to a hangar full of U.S. troops.

But Obama also made time for something else, something personal. Just after 2 a.m., the president slipped away for a meeting that he had deliberately kept off his public schedule.

In a small, private room, 15 mortuary affairs soldiers waited to greet him. These were the soldiers who prepared the bodies of troops killed in battle for their trip home. To blunt the overpowering stench of death, they wore masks when they worked, burned their uniforms regularly and dabbed Vicks VapoRub under their noses.

Now that they were about to meet Obama, members of a unit used to working in the isolation of war’s grim aftermath all had the same question: Of all the soldiers in Afghanistan, why had the president asked to see them?

Obama’s visit came in the spring of 2012, just months before his election to a second term, in which he had promised to speed America’s exit from its post-9/11 wars. Since then, a new war has erupted, while an old war continues. Today, the president faces mounting pressure to send more troops to Iraq to help in the battle against Islamic State extremists.

His decision will be influenced by the counsel of his generals. It will also be guided by more private moments in his wartime education — at the bedside of wounded troops; on the tarmac of Dover Air Force Base, where the war dead return to American soil; and in that small room with the mortuary affairs soldiers one middle of the night in Afghanistan.

Discussions of war and peace in Washington often revolve around abstract questions of policy and national interest. Rarely mentioned are the human costs of war and how they weigh on a commander in chief. “It’s probably the least appreciated and most difficult part of leadership,” said Michele Flournoy, who served at the top levels of Obama’s Pentagon. “It’s not an abstraction, and, if you have any doubt, it eats at you, because the human costs are very real.”

Every president experiences war differently. Some become consumed with its politics and special ability to unravel prized domestic agendas. Others see in war an opportunity to reshape the world, build a legacy, deter future enemies.

As a wartime commander, Obama has often focused his words on war’s tragedies and his actions on ratcheting down risks to troops. “We believe it is a national security objective not to be losing service members in wars,” said Ben Rhodes, the president’s deputy national security adviser for strategic communications.

Obama has sent commandos on dangerous raids to save American hostages facing imminent death in Iraq and Syria and to disrupt active terrorist plots. But outside those narrow missions, he has been unusually cautious about putting U.S. troops in harm’s way — especially in Iraq, where American troops are today restricted from operating as close to the front lines as their Canadian and British counterparts, according to senior U.S. officials.

The president’s Republican critics say that Obama’s caution undermines the military’s ability to fight and achieve his stated goals.

“He never had the steel and fire to be a wartime president,” said Eliot Cohen, who was a senior State Department official in the George W. Bush administration and is now a professor at Johns Hopkins University’s School of Advanced International Studies. “You have to be able to give orders to send people into harm’s way. You have to have the hardness to make those decisions.”

Obama’s closest aides counter that rather than distancing himself from — and hardening himself against — the costs of war, the president’s impulse is to understand as intimately as possible the human consequences of his decisions.

And so in the quiet of 2 a.m., he arrived for his meeting with the mortuary affairs soldiers, who had just received word that the body of a 23-year-old sergeant, killed in a Taliban ambush in southern Afghanistan, was on an inbound plane. Obama thanked them for their diligence and posed for a group picture.

“He told us how important our job was,” recalled Sgt. 1st Class Jorge Cruz, “and said that our work had not gone unnoticed.”

Twenty minutes later, Obama left to prepare for a prime-time speech to the nation in which he would outline his plan to end the U.S. involvement in the Afghan war. The mortuary affairs troops strode out to the air base’s tarmac, where the body of Sgt. Nicholas Dickhut was waiting for them. They documented his wounds and searched his body for pictures, letters, a pocket Bible or other talismans that could be sent home to his family.

They were still working on him when Obama, speaking to a single camera in an empty airplane hangar, delivered his address.

“As president, nothing is more wrenching than signing a letter to a family of the fallen, or looking into the eyes of a child who will grow up without a mother or father,” Obama said. “I will not keep Americans in harm’s way a single day longer than is absolutely required for our national security. But we must finish the job we started in Afghanistan and end this war responsibly.”

The troops finished their work about 8:30 a.m. By then, Obama was already on his way back to Washington, having left for security reasons before the sun rose.

Three weeks later, a letter from the president arrived at the Rochester, Minn., home of the dead sergeant’s mother. “In life your son was a shining example of all that is best in our land,” Obama wrote. “In rest, may he find the peace we all seek.”

From Oslo to West Point

Before he had much firsthand experience with the costs of war or the burdens of being commander in chief, Obama delivered a speech about both.

In December 2009, just days after he issued orders sending 30,000 new troops to Afghanistan, Obama flew to Oslo to accept the Nobel Peace Prize.

To prepare for his Afghanistan decision and Nobel address, Obama visited Dover Air Force Base to witness the return of 18 Americans killed in Afghanistan. He met with families of deceased troops and asked his speechwriters to pull together a packet of writings about war by people he admired: King, Gandhi, Churchill, Saint Thomas Aquinas, Reinhold Niebuhr.

“I’m responsible for the deployment of thousands of young Americans to battle in a distant land,” Obama said in Oslo. “Some will kill, and some will be killed. And so I come here with an acute sense of the costs of armed conflict — filled with difficult questions about the relationship between war and peace.”

That was war as the president imagined it to be. His real-world education in the human consequences of his decisions would take place over the next several years, and, for the most part, he would reveal little of what he was learning. Obama rarely displays strong emotions, even during discussions of war. The trait has bothered some of his most senior advisers, especially those closest to the military.

“One quality I missed in Obama was passion, especially when it came to the two wars,” former defense secretary Robert M. Gates wrote in his autobiography. Bush would sometimes tear up when meeting with the families of deceased soldiers. “I worked for Obama longer than Bush, and I never saw his eyes well up,” Gates wrote.

Obama’s reserve left his top advisers guessing how he was handling the growing American losses in Afghanistan, which more than tripled from 155 deaths in 2008 to nearly 500 during 2010. Those who backed his troop surge recognized that the president had made a tough decision on Afghanistan that ran counter to his instincts and the advice of his most trusted civilian advisers.

“Half his staff and the vice president were telling him that he had made a mistake,” said a former senior administration official, who, like other administration officials, spoke on the condition of anonymity to talk about internal deliberations. “They were constantly hounding him.”

Others who were sure that the surge was a mistake wondered how the president’s regular visits with the wounded and maimed in military hospitals were influencing his decisions. “It’s very hard to go to Walter Reed if you think you are just sustaining the status quo or a stalemate,” said a member of the president’s senior staff.

One glimpse into Obama’s thinking came last year at the U.S. Military Academy at West Point, where the president outlined his new strategy for fighting terror.

Obama questioned the wisdom of large-scale military occupations that stir local resentments and carry a heavy price at home. Instead, he said, he would employ small detachments of military advisers to work with local partners away from the front lines.

Just as he had in Oslo, Obama talked about the horrors and human costs of combat. This time, though, he wouldn’t need to draw on the abstract — the wisdom of Churchill, Niebhur or King.

In a brief section that Obama wrote into his speechwriter’s draft, the president noted that he had announced his Afghan surge nearly five years earlier at West Point. Four soldiers in the audience that day had been killed in Afghanistan following his orders, and many more had been maimed.

“I believe America’s security demanded those deployments,” Obama told the crowd of soon-to-be second lieutenants, whose job was now to follow his orders. “But I am haunted by those deaths. I am haunted by those wounds.”

Mosul and American lives

Obama had barely finished delivering his West Point speech when thousands of Islamic State extremists seized Mosul, Iraq’s second-largest city, sweeping aside an Iraqi army that had been the beneficiary of billions of dollars in American training and equipment over the past decade.

The president has responded with more than 2,100 airstrikes in Iraq and Syria and dispatched more than 1,000 military trainers and advisers. Those troops are restricted from taking part in combat and are relegated to working with Iraqi forces at secure bases or rear-area headquarters.

Obama set the limits on American military involvement to prevent rash or unnecessary escalations that might result from U.S. casualties, said White House officials. “Whenever an American is harmed, it creates pressures to do something in response,” Rhodes, the deputy national security adviser, said. “You saw that — even though they were not service members — with the hostages that were killed by [the Islamic State].”

The restrictions have led some senior military officials to ask whether the United States is approaching a zero-casualty moment, similar to the one that defined U.S. foreign policy under President Bill Clinton.

Then, the pressure to eliminate combat losses was fueled by a belief that Americans would not tolerate the deaths of their sons and daughters in the Balkans, Somalia and Haiti, none of which were seen as essential to the nation’s security. Some top generals at the time argued that these post-Cold War missions sapped U.S. firepower and prevented the military from focusing on more pressing threats.

Today, there’s a broad consensus among Republicans and Democrats that the Islamic State, whose forces span the Iraq-Syria border, must be defeated. “Our interest is in making sure Iraq is whole and not riddled with safe havens that can be used to hit us,” said Denis McDonough, Obama’s chief of staff.

The first major battle in that campaign is expected to take place this spring or summer, when Iraqi army forces will launch an offensive to drive Islamic State rebels from Mosul.

Senior U.S. officials said the credibility of the Iraqi government and its rebuilt army hinges on the offensive’s success. “Mosul has an iconic meaning to the Iraqis, an iconic significance,” said a senior U.S. official involved in planning for the attack. “We’ve got something big brewing out there . . . and it’s in our interests that we win.”

Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, has said that if he determines that the Iraqis need front-line help from U.S. combat advisers to retake Mosul, he will make that recommendation to Obama.

“We’re certainly considering it,” he told lawmakers late last year.

Front-line American combat advisers would help strengthen the resolve of untested Iraqi troops. “We call it the steel rod up the backbone,” said the senior U.S. official. “It is a remarkable thing to see.” Front-line combat advisers could also help improve the accuracy and effectiveness of American airstrikes as Iraqi forces surge into Mosul.

The decision will fall to Obama, who his advisers say will weigh a series of questions.

Some will be of a military nature: If U.S. advisers help lead the fight from the front, providing the “steel rods” up the Iraqis’ spines, will the Iraqi forces be able to hold and sustain their gains when the U.S. advisers leave?

Some will hinge on Iraqi politics: After the battle, will the Shiite-dominated Iraqi government be able to win the support of Sunnis in Mosul, whose disaffection from Baghdad provided the opening for the Islamic State’s victories last summer?

Ultimately, a war-weary Obama’s decision could hinge on his answer to a single, personal question.

It’s a question only this commander in chief can answer: After 11 years of almost nonstop war in Iraq, is driving the Islamic State from Mosul worth any more American deaths?