WASHINGTON — More than half of the 2.6 million Americans dispatched to fight the wars in Iraq and Afghanistan struggle with physical or mental health problems stemming from their service, feel disconnected from civilian life and believe the government is failing to meet the needs of this generation’s veterans, according to a poll conducted by The Washington Post and the Kaiser Family Foundation.

The long conflicts, which have required many troops to deploy multiple times and operate under an almost constant threat of attack, have exacted a far more widespread emotional toll than previously recognized by most government studies and independent assessments: One in two say they know a fellow service member who has attempted or committed suicide, and more than 1 million suffer from relationship problems and experience outbursts of anger — two key indicators of post-traumatic stress.

The veterans are often frustrated with the services provided to them by the Department of Veterans Affairs, the Pentagon and other government agencies. Almost 60 percent say the VA is doing an “only fair” or “poor” job in addressing the problems faced by veterans, and half say the military is lagging in its efforts to help them transition to civilian life, which has been difficult for 50 percent of those who have left active service. Overall, nearly 1.5 million of those who served in the wars believe the needs of their fellow vets are not being met by the government.

“When I raised my right hand and said, ‘I will support and defend the Constitution of the United States of America,’ when I gave them everything I could, I expect the same in return,” said Christopher Steavens, a former Army staff sergeant who was among 819 vets polled. He served in Iraq in 2003 and in Kuwait two years ago, where he was injured in a construction accident. Upon leaving the Army last summer, he filed a claim with the VA, seeking medical care and financial compensation. He has not yet received a response.

“It’s ridiculous that I’ve been waiting seven months just to be examined by a doctor — absolutely ridiculous,” he said.

Even so, the vast majority of recent veterans are not embittered or regretful. Considering everything they now know about war and military service, almost 90 percent would still have joined.

“What we did had a positive impact there,” said Texas Army National Guard Sgt. David Moeller, who spent two year-long tours in Iraq. “I don’t regret it. It’s something I’d do over and over again.”

Drawing upon detailed interviews with randomly selected war veterans across all military branches, including those still serving and those no longer in the military, the nationwide poll provides an unprecedented glimpse into the lives and attitudes of modern warriors — an undrafted, all-volunteer cadre, most of whom signed up in the wake of the Sept. 11, 2001, attacks. That force, drawn from nearly every county in the nation and often sent on multiple year-long combat tours, has included more than 280,000 women and thousands of 18-year-olds.

Although more than 6,800 U.S. service members were killed in Iraq and Afghanistan, advancements in body armor, transportation and battlefield medicine gave troops a better chance of coming home than any other generation of war fighters.

“They have come back to a nation that has embraced them — warmly, strongly, positively — and put tremendous value and appreciation into their service,” Defense Secretary Chuck Hagel said in an interview. “That is so important.”

Many are thriving — they are attending college, paid in full by the post-9/11 G.I. Bill; they are finding employers who covet their leadership skills and work ethic; they are receiving the medical attention they need. But the poll also found that hundreds of thousands of others feel they have been left behind on an uncharted postwar landscape, fighting for benefits, struggling to land a job, wrestling with psychological demons unleashed by combat or coping with shattered families.

Their responses reveal nuanced views of their lives, their service and their treatment by the government. Almost three in four believe the average American appreciates their service, but fewer — only 52 percent — like talking about their wartime experiences with casual acquaintances or strangers. Nearly 90 percent performed actions in Iraq or Afghanistan that made them feel proud, yet only 35 percent believe both wars were worth fighting.

“I don’t find that to be in any way a contradiction of data,” Army Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, said in an interview. “I think that this aspect of service, and being true and trustworthy to the man or woman on your left or right, is probably what mostly drives the 90 percent figure. They’re proud of what they did. They believe they did their job, and potentially the elected governments of Iraq and Afghanistan didn’t do theirs.”

Some of their present-day challenges — securing a well-paying career and coping with credit-card debt — mirror travails of American society as a whole, but other needs are unique consequences of this century’s conflicts: diagnosing and treating traumatic brain injury, acquiring technical skills to compete in a transforming economy and addressing the stress on families from repeated combat tours. More than 600,000 Iraq and Afghanistan veterans who have become partially or totally disabled from physical or psychological wounds are receiving lifelong financial support from the government, a figure that could grow substantially as new ailments are diagnosed and the VA processes a large claims backlog.

“What is different about this generation? We’ve asked them to do a lot more, in a smaller serving force, in some of the longest wars in our history,” VA Secretary Eric Shinseki said in an interview. Multiple deployments have created what he calls “a compounding effect” to health problems and combat stress, with an unknown overall cost. “There’s more work to be done in terms of research and understanding of what the full impact is going to be.”

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For many vets, their times in Iraq and Afghanistan were searing experiences. One in three think about their deployments daily. Among them is Nicholas Johnson, a former specialist in the Arkansas Army National Guard, who spent a year in Iraq starting in 2006. His platoon was ordered to fill roadside bomb craters, which required him to jackhammer asphalt while wearing 50 pounds of body armor and gear. He returned home with a fractured vertebra, three fused disks in his back, ringing ears and debilitating post-traumatic stress because of the frequent carnage he witnessed on Baghdad’s roads.

“I can’t get a good job now because . . . I have to be upfront and say I have this disability, I have a tore-up back,” he said. “So now, the factories here in Topeka, where I live now, they’re like: ‘Oh, wow, he has military experience. Great. He has managerial experience. Oh, that’s good. Some college — all right. Oh, he tore his back up. Can’t do that, you know.’ ”

Johnson, who is 32 “but going on 60,” confronts the toll of his service on his drive to a just-over-minimum-wage job at Lowe’s, when he has to avoid Interstate 70 because it reminds him of Baghdad’s insurgent-riddled airport road, when he panics at the sight of trash on the street because that’s what Iraqi guerrillas employed to conceal explosives, when he pops painkillers and anti-anxiety pills, when he has to use a cane to walk or ask his fellow clerks for help moving boxes.

“I left the war zone,” he said, “but the war zone never left me.”

This generation’s veterans are more diverse than any other contingent America has shipped to war. Thirty-five percent are non-white, more than one in 10 are women and a quarter are now 40 years or older.

But much of the force remains homogeneous: Half are Southerners, two-thirds lack a college degree and almost six in 10 live in a non-urban area.

More than eight in 10 vets served at least one tour in Iraq or in support of that war. Of those deployed to Iraq, 47 percent were sent on two or more deployments, and 29 percent — more than a half-million service members — spent two years or more in the strife-torn country. By contrast, 29 percent of vets who deployed to Afghanistan had two or more tours, and 16 percent spent at least two years there.

The entire group of 2.6 million post-9/11 vets includes hundreds of thousands of troops who did not serve within the borders of Iraq or Afghanistan but who worked in support of operations in those nations from bases and ships in the Middle East and South Asia. Those deployments often were arduous and risky and involved separation from families. In tallying those who served, the Defense Department does not distinguish between them and those who walked on the soil of Iraq or Afghanistan.

More than 730,000 went as members of the reserves or National Guard, forcing them to place their civilian lives on hold for as long as a year, sometimes more than once. It was the largest use of both forces since World War II, greater even than during the Vietnam and Korean wars.

The vets hail from families where service in the military is tradition: More than four in 10 have fathers who were in the military, and half have at least one grandparent who was. Almost 40 percent say all or most of their friends have served in the military. By contrast, a national Kaiser Family Foundation poll conducted in December found that 32 percent of U.S. adults had “hardly any” or no friends who have been in the military.

Slightly more than half yearn for their time in the wars. Of them, almost two-thirds cited the bonds they forged with fellow military personnel. “It was a unique time,” said Kevin Ivey, a retired Army helicopter pilot who spent a year in Afghanistan starting in 2004. “I miss my crew, the folks I was with, the organization. You make lifelong friendships in war.”

Many vets see themselves as a cut above the rest of American society, as noble volunteers who stepped up to promote and protect U.S. interests while the rest of the nation went about its business as usual. Sixty-three percent think service members are more patriotic than those who are not in the military; 54 percent think the average member of the military has better moral and ethical values than the general civilian population.

Almost seven in 10 feel that the average American routinely misunderstands their experience, and slightly more than four in 10 believe the expressions of appreciation showered upon veterans — often at airports, bars and sporting events — are just saying what people want to hear. More than 1.4 million vets feel disconnected from civilian life.

“A lot of vets find it easier to talk to each other, especially about their wartime experiences,” said Jennifer Smolen, who served in Iraq for a year with an Army Reserve engineer unit and is now an active member of a Seattle area American Legion post. “There’s a feeling that civilians who weren’t there just don’t get it.”

Moeller, the Texas National Guard sergeant, returned from his first deployment to Iraq with back pain so severe he had to sleep sitting upright. In 2009, when his unit was mobilized again, he “could have waved the medical flag.” But he wanted to head back out with his buddies “to complete the mission, because that’s what I took an oath to do.” So he kept quiet and toughed it out.

When his unit was called up again in 2012 to go to Afghanistan, he once again tried to deploy. “I can make it one more time,” he thought to himself. But an Army doctor thought otherwise. “Isn’t it time you started taking care of yourself?” he suggested.

According to the Defense Department, 51,908 service members were “wounded in action” in Iraq, Afghanistan or in missions to support the wars. That tally doesn’t include Moeller — or hundreds of thousands of others — because the Pentagon counts only those injured as a “direct result of hostile action.” If a wound did not occur on a combat operation, or it was the result of an accident, or it was caused by wearing armor every day for a year, it does not make the list.

But in Iraq and Afghanistan, where there were no front lines, where improvised explosive devices were the enemy’s weapon of choice, where troops wore bulky protective gear most of the time, wounds that do not fit the military’s classic definition became the norm. Traumatic brain injury. Persistent ringing in the ears. Elevated blood pressure.

Once troops returned home and the adrenaline ebbed, they began to confront the cost of all they wore to protect them, of the bone-jarring trips in mine-resistant trucks, of inhaling desert sand pulverized into jagged particles by armored vehicles. Back pain. Blown-out knees. Headaches. Persistent coughs.

For more than 1.1 million vets, serving in the wars has left them in worse physical health, according to the poll. Eighteen percent — about 470,000 current and former service members — reported being seriously injured while deployed to Iraq, Afghanistan or in support of the wars. Some of those wounds have been profoundly life-altering — lost limbs, widespread burns, massive brain damage. Others are more prosaic, often the results of accidents or wear and tear on the body, but nonetheless have saddled veterans with enduring pain.

Edna Harris, a former Army sergeant who deployed twice to Iraq, fell out of a five-ton truck, injuring several vertebrae. When she went to the medical clinic on her forward operating base, all she received were some Motrin pills. Harris is now back home in Jacksonville, Fla., but persistent back pain limits her activities. “I can’t play with my son like I want to,” she said. “I can’t run after him or throw a football with him.”

Kevin Ivey, a retired Army chief warrant officer, flew helicopters for a year in Afghanistan. Strapped into a vibrating aircraft for 10 hours a day while wearing body armor led to diagnoses of nerve damage and bone degeneration in his back and neck. “It tore me up pretty good,” he said.

Justin Peachee, a sergeant in the Texas Army National Guard, spent a year as an infantryman in Iraq, hauling a heavy rucksack, rifle and ammunition over his armored vest. His knees now have worn-out cartilage and leaking fluid sacks. He is 26. “I just want my knees to be my knees again,” he said. “I don’t want grandpa knees at this point.”

One in three veterans surveyed by The Washington Post and Kaiser said the VA or the Defense Department has determined they have a service-connected disability, a ratio that is almost identical to the VA’s overall tally. Most have no scars. As with Peachee, Ivey and Harris, their physical wounds are under the skin, or they are inside the brain.

The poll found that the wars have caused mental and emotional health problems in 31 percent of vets — more than 800,000 of them. When more specific questions were asked, the rates increased: 41 percent — more than 1 million — report having outbursts of anger, and 45 percent have relationship problems with their spouse or partner. Both are indicators of post-traumatic stress and could suggest that rates of affliction may be higher than the government has forecast.

Although The Washington Post and Kaiser did not ask respondents the full battery of questions typically used to make post-traumatic stress diagnoses, previous studies conducted for the Pentagon, including one by the Rand Corp. in 2008, have estimated rates of post-traumatic stress at 14 percent. Time may explain some of the difference: Every service member experiences the stress of war differently, and some do not feel it for years.

For Adam Schiele, a former active-duty military police officer in the Army, it has taken a decade. In recent months, he has been haunted by an Afghan man’s plea for medical assistance for his badly wounded niece at the gate of a U.S. base — and the initial refusal of American medics, which he describes as callous, to examine the girl. Nothing went boom. Nobody died. It happened a decade ago. But the incident was jostled from the recesses of his mind in the wake of an assault on a fellow guard at the federal correctional institution where he works. Since then, Schiele, who now finds the memory more vivid than ever, has been placed on disability leave.

“I’m sitting at home, hoping it will go away,” he said. “It’s disheartening. It’s discouraging. It makes you feel inadequate.”

Troops “don’t need to be classified as wounded in action to have been wounded,” he said. “A lot of us got hurt. Some more serious than others, but a lot of us sacrificed part of our bodies out there.”

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Iraq and Afghanistan vets are making unprecedented use of the Department of Veterans Affairs, largely because of an Obama administration decision to provide five years of free VA health care to all of them. Of the 1.7 million who are no longer serving in the active, reserve or National Guard forces, more than 1 million have obtained health-care services at least once from the VA since 2002 and about 45 percent of them have sought compensation for service-related disabilities. By comparison, about 21 percent of those who fought in the 1990-91 Persian Gulf War filed similar claims.

The difference between the nearly half seeking compensation and the third who have received it may help to explain why almost six in 10 vets believe the VA is doing a “only fair” or “poor” job in meeting the needs of their comrades.

Under President Barack Obama, the VA’s budget has grown by more than 60 percent over the past six years, although congressional overseers and veterans’ organizations complain that the department continues to be hobbled by what they consider a bloated and inefficient bureaucracy.

“There’s always room for improvement,” said VA Secretary Shinseki, who believes the widespread frustration is rooted not in the quality of service provided by the VA but by the delay in processing disability claims, which he has pledged to eliminate by the end of next year. Despite the backlog, he emphasized that this generation of veterans has been provided benefits, including college tuition reimbursement through the G.I. Bill and free health care, “in ways that didn’t happen after Vietnam.”

“We’ve asked a lot of this generation,” said Shinseki, a Vietnam War veteran. “We owe it to them.”

Overall, more than half of vets say the government is not doing a good job in addressing the requirements of this generation of veterans. But when asked to rate their own treatment, almost 60 percent say the government’s response is “excellent” or “good.” Vets give even higher marks when it comes to their own health care, with more than eight in 10 saying their physical, mental and emotional needs are being well met.

They are far less sanguine about the transition to civilian life. Half think the military is not doing enough to help vets adjust to the world beyond their U.S. and overseas bases, where men and women who never had to worry about where to live or how to write a resume now must learn to navigate American streets and survive job interviews. Just as many say their own transition to civilian life was either somewhat or very difficult.

Asked to describe why, in their own words, slightly over a quarter said it was because of employment-related issues, such as adjusting to a civilian-run workplace. A similar percentage said the principal challenge involved the profound differences between civilian and military life. Among those still in the military, 43 percent expect a difficult transition to civilian life.

“There are those that are very much in need of help, but the majority — the vast majority — are less in need of a handout than simply a handshake, an opportunity,” said Joint Chiefs Chairman Dempsey.

Hagel said the military needs to do more to educate business leaders about the skills veterans can provide to U.S. corporations. “There’s where we’re not doing enough,” he said. “We need to keep working at it.”

Overall, two-thirds of vets feel they possess the skills and education required to be competitive in the civilian job market. But there is a significant difference in views between officers, who are required to have at least a bachelor’s degree, and enlisted personnel, most of whom do not have a college degree. Almost a quarter of current and former enlisted troops think the skills they have acquired in the military have no use in civilian employment; only 2 percent of officers feel the same way.

Enlisted vets also report more severe economic challenges. Forty-three percent of them have taken an extra job or worked additional hours because they need the money, compared with just 16 percent of officers. A quarter of enlisted members have had trouble paying their rent or mortgage; only 11 percent of officers say the same.

Upon leaving the Marine Corps in 2012, April White figured she would find a steady job to support herself and her then-7-year-old son in North Carolina. Although enlisted, she had been a sergeant with supervisory experience, and she had military logistics skills, honed during a 2007 deployment to Iraq. She sent out a raft of applications for secretarial jobs and transportation-related work. She landed just one interview, with an employer who was seeking someone with a college degree, which she lacks.

After four months on unemployment assistance, she signed up for the only option she could find — as a contractor in Afghanistan. “I thought once I got out [of the Marines], life was going to be normal,” she said. Instead, she had to explain to her son that she was going away again. “I told him, ‘I don’t want to go to Afghanistan, but I need a job.’ ”

Now back in Jacksonville, N.C., White has opted to take advantage of the post-9/11 G.I. Bill to remain close to home, pay her bills and attend a nearby college, where she is taking engineering classes. The VA-administered program, which pays for tuition and provides a stipend for books, school supplies and housing, has been used by almost half of all Iraq and Afghanistan vets. For many, it has served as a hyperbaric chamber to adjust to civilian life, allowing them to stay busy and avoid poverty as they set out to find a post-military career.

“The days of getting out of the military and getting a job — a good job — right away are over,” White said. “You have to study, and you have to be patient — and you have to be lucky.”

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Despite their overwhelming pride and negligible regret, the veterans look back on the necessity of the conflicts with decidedly mixed feelings. Only 53 percent of them believe the war in Afghanistan has been worth fighting, and just 44 percent say the same for Iraq. Slightly over a third — almost 900,000 vets — “strongly” believe the Iraq war was not worth it.

Those figures are moderately higher than the population as a whole, but they nonetheless reveal a fundamental nuance in attitudes among the all-volunteer military: Many among this generation of vets regard their service as a profession — almost half signed up intending to serve for at least 20 years — and they have divorced their individual missions from the worthiness of the overall wars.

“Right, wrong or indifferent, it was something we signed up to do,” said Kenneth Harmon, a retired Marine master sergeant who served for 23 years and deployed to Iraq and Afghanistan. “It was our job. We got orders. We followed them.”

That detachment was easier for those who saw value in the wars. “When I see people smile because we’re there, when I see kids happy that there are American troops with boots on the ground over there, it had always reaffirmed my belief that we were doing the right thing,” said Santino Fort, a retired Air Force technical sergeant who deployed twice to Afghanistan and once to Iraq.

Others have grown increasingly frustrated as they have heard of developments in both nations, of Afghan President Hamid Karzai refusing to sign a bilateral security agreement with the United States, of the Iraqi city of Fallujah falling to al-Qaida militants spilling over from Syria. For Peachee, the National Guard sergeant with “grandpa knees,” Iraq now feels “like a big waste of time.”

“We turned it over, and it’s gone back to chaos and anarchy,” he said. “The government and the citizenry don’t have respect for anything that we fought for.”

But that has not soured his view of the Guard. “I joined because I want to do interesting things,” he said. A few months ago, he re-enlisted for six more years.

The military, which was showered with money to grow its ranks and acquire new equipment over the past decade, probably will be far smaller when his enlistment ends. And it almost certainly will include more women serving in ground combat roles, a change that half of all post-9/11 vets believe will “not make much difference” on military effectiveness.

Current and former members of the Navy were most supportive — almost two-thirds of them say the Pentagon’s decision to roll back a ban on women in combat positions will not affect war fighting — while the Marines were the most skeptical: 45 percent of them feel that doing so would have a negative impact on the force.

Although women were kept from ground combat jobs in Iraq and Afghanistan, many found themselves in harm’s way. Thousands of others served in key positions on headquarters staffs, in hospitals and within support units. Some were generals.

Despite fielding the most gender-integrated force in U.S. history, almost half of female vets say the military is not doing enough to prevent sexual assault among service members. Among men, four in 10 share that view.

In a recent VA survey of 1,500 women who deployed to Iraq and Afghanistan, one in four said they experienced sexual assault — defined as any unwanted contact from groping to rape — during their deployments.

“Just being a woman was an additional stressor,” said Melissa Ross, one of the Post-Kaiser poll respondents, who deployed to Afghanistan as a staff sergeant three times and always wore an extra knife strapped to her back. “Just being a female. Just the amount of fear of ‘What if?’ — ‘ What if you have that one airman or Marine or Army guy who doesn’t know you and looks at you just as a female?’ That was the biggest stressor for me daily. That crossed my mind way more than, ‘What if we hit an IED?’ ”

When it comes to their most-senior commander, the vets decisively prefer George W. Bush to Obama. Only a third approve of the way Obama is handling his job, and 42 percent of them think he has been a good commander in chief despite his decisions to bring troops home from Iraq, wind down the war in Afghanistan and increase resources for veterans. By contrast, nearly two-thirds of them think Bush, who launched both wars, was a good commander in chief.

Their views of the two presidents appear to be shaped less by political affiliation than by concern over the Obama administration’s plans to reduce the size of the military, trim benefits for future service members and curtail the purchase of some costly new weapons systems. Nearly half of vets regard themselves as political independents. Among those who identify with a party, the Republican-Democratic split is 27 percent to 17 percent.

The vets’ political philosophy is more striking: 44 percent describe themselves as conservative, and 29 percent say they are moderates. One-fifth of them are self-described liberals.

When asked if they would be willing, in these times of federal government deficits, to support a reduction in benefits to future generations of troops, they are overwhelmingly opposed, even if it contributes to future budget shortfalls. Only 12 percent feel that benefits should be curtailed, despite warnings from Defense Department leaders that growing health-care and pension costs are eating into funds for training and equipment.

When it comes to sharing the responsibility of care with the private sector, 63 percent of vets think that they merit special advantages from employers when applying for jobs. By contrast, four-fifths of all Americans feel employers should provide advantages to vets during the hiring process, according to a separate Kaiser Family Foundation survey conducted in December.

The military’s retirement program awards pensions and lifetime family health care to those who have served 20 years or more. The system, which provides nothing to those who spend less than two decades in uniform, has left many Iraq and Afghanistan vets — including those who signed up after September 2001, were deployed multiple times but then chose to leave the military — without any retirement benefits.

The vets, however, do not see it as a trade-off. More than half feel the 20-year system provides “about the right amount” of compensation to retirees. But they also want to increase benefits to those who served in the wars and then left before hitting the two-decade mark. Slightly over half say that group receives fewer benefits than they deserve.

Among them is Jeffrey Arena, a former Army sergeant in the 101st Airborne Division who had two year-long combat tours in Iraq and one in Afghanistan. He had planned to serve 20 years in the Army and then use his infantry skills to land a law-enforcement job. Last year, however, his hip and leg began to hurt during his morning physical-fitness routine. A doctor on Fort Campbell, Ky., told him that a leg injury he suffered in Iraq during a 2006 mission to pursue insurgents was far more serious than he had been told by field medics at the time: He had fractured his femur and torn cartilage in his hip.

The military offered him a hip replacement, which he turned down. “I’m only 35, and I don’t want a hip replacement at 35,” he said. “There would be no more running or jumping. I have three kids. I want to be active with them.”

Replacement or not, the diagnosis spelled the end of his military career. Because he was unable to pass his annual physical-fitness test, the Army moved to retire him on medical grounds. But it deemed him only 20 percent disabled, which meant that he would be ineligible for a military pension or lifetime health coverage, even though he spent 38 months at war and suffered a serious injury while deployed.

“I beat up my body for this nation,” he said. “It should count for something.”

Arena’s last day as a soldier was Feb. 13. In the months leading up to his separation from the Army, he sought to participate in a military-funded internship program that allows departing troops to explore new civilian careers. The initiative has been touted by Army generals as a key step in the transition from military life. But when he asked the commander of his unit for permission, he was turned down. “They told me they didn’t want to pay me for working at another job,” he said. “The Army says, ‘You can,’ but my command said no.”

Worried that his hip injury will disqualify him from law enforcement jobs, he plans to head to flight school in Arizona, where he will live out of a trailer for a year while his family remains at their home in Kentucky.

“In the Army, you’re taught to never leave a man behind. Well, they’ve basically left a man behind,” he said.

“It was easy to send us off to war. Taking care of those who need help — and there are lots of us — will be much tougher. But if our nation is going to send us to war, it has a responsibility to do right by us when we come home.”