A younger man sat beside me while I was off to myself smoking a cigar and asked if I had another. I did, and he was welcome to it. He’d earned it.

His little son made a yuck face when he put fire to it and began puffing on it.

“He doesn’t like this,” he said. “He doesn’t understand that this is what we do when we come home.” That was only a few days before.

“People keep thanking me for what I did, and they act like I’m a hero. I don’t understand that,” he said.

He talked about what he’d done in Iraq, and there was a number he kept repeating in a tone of voice you couldn’t identify unless you’d heard it before and had an idea of where it comes from. I recognized it immediately.

A friend who’s my age told me he’d reached the point in Vietnam where he enjoyed killing and actually looked forward to it. Then, in the night’s loneliest hours, he wondered what it was doing to his soul. It tormented him, and he was afraid of going mad.

Another man told me he felt an absolute lack of remorse at killing armed North Vietnamese soldiers, but had great sympathy for those who were badly wounded and in agony, or in fear for their lives while being held prisoner.

How can such contrasts exist in someone’s mind? For Americans, that’s how it works. During the Berlin Airlift, American aviators risked their lives to bring food and fuel to a city they all but destroyed three years earlier. They attached tiny parachutes to candy and dropped it to children, who as senior citizens remember and still love them to this day.

The same Americans who invaded Iraq, defeated its military and overthrew its government also taught Iraqis the basics of health and emergency medical care. They built hospitals and schools, only to see them blown up by terrorists ... then rebuilt them. They’ve bled and died in an effort to secure someone else’s freedom — but that’s nothing new for Americans. I’m told that the Iraqi kids adore our troops.

We Americans possess a blend of ferocity and compassion that may be unique.

The overriding concept that guides our moral philosophy is that human life is precious. However, history’s bitter lessons show that America needs more than just good will to survive. That’s why we teach some of our young people how to take human life with greater proficiency than our enemies can manage. (As the saying goes: If you can read this, thank your teacher. If you can read this in English, thank a veteran.)

Mix this capacity for violence with the reverence for life that our culture demands, and it’s little wonder many are haunted by the results — particularly if they’ve also seen their friends maimed and killed. More Vietnam veterans have now committed suicide than died in actual combat. So did an Iraq veteran who had been unable to prevent an Iraqi child from picking up a booby-trapped weapon.

Our sense of humanity can put us at a disadvantage in dealing with those for whom human life has little significance. Someone familiar with the Chosin Reservoir in Korea told me, “Two hundred American soldiers who want to live don’t have much chance against a human wave attack by 5,000 Chinese soldiers who don’t care if they die.”

Regardless of what my young friend may have felt about the performance of his duty in Iraq, there can be no doubt that his enemies would have rejoiced at taking his life — even if it cost their own lives.

“Ask yourself this,” I told him. “How many of your buddies lived to come home to their families because of what you did?”

“Nobody looks at it that way,” he said. “They don’t understand.”

He said he had to go back to his civilian job the next day.

“But it’s not important,” he said. “Not any more.” He pointed to his young son and said, “That’s what’s important.”

Then he added, “But he doesn’t understand. Nobody understands. How can I ever tell him about it in a way that he’ll understand?”

I suggested this: “When he’s old enough to begin asking, he’ll be old enough to start hearing about it. You don’t have to tell him all of it at once, but a little bit at a time. And you and his mother pray that he never has to find out for himself what it’s like.”

My friend is of strong character, and his family and friends are good people. They’ll help him reassign things like his civilian job to their proper level of importance, and they may not even realize it’s happening. Millions of others have made the same transition.

It’s a good sign that he’s already able to talk about it. A remarkable change came over my Uncle Abe Goldsworthy when he began telling me about his war as a World War II Army medic in Europe.

I called him on Veterans Day some years ago to thank him for what he’d done. He hadn’t wanted to talk about it before, but that night I began to learn how proud he was to have been an American soldier. Each time we met after that, and we were alone, he had something new to tell me. It always seemed to leave him a little more at peace with the terrible wounds he had suffered ... both physical and mental.

“You have no idea how important it is to be able to talk to someone who cares and wants to listen,” a friend of mine said after describing an episode he survived in Vietnam, but someone else didn’t. Like some of what my uncle told me, its nature will prevent me from ever writing about it.

Take people who are young — maybe 18 or 19 years old and away from home for the first time — and thrust them into an environment that’s horribly different from anything they’ve ever experienced or could have imagined, and for which no training could have adequately prepared them.

If they survive, they return to a once-comfortable world that’s not like the one they remember ... the only catch is, nothing has changed but them. Even if they are physically healthy, they may have difficulty coping.

For some, all that’s left is a lasting hatred, bitterness or despair. For others, however, it was simply an important job to do or a chance to serve their country. A few have told me it was a great adventure. One said he’s been busy, but bored, so far in Iraq; I told him I hope it stays that way, and he agreed.

Each is different ... yet somehow, they’re all the same.

If it’s important for them to talk, it’s equally important for someone to listen. That’s the only way to find and address the mental scars that often remain, even if there was physical damage and it has healed.

A veteran can roll up his sleeve and show you an old war wound, but the Post-Traumatic Stress Disorder that infects every aspect of his life is much harder to see. So is the Survivor’s Guilt felt by those who don’t understand why they came home, when others didn’t.

My friends who are Vietnam veterans don’t understand why they were so often treated with derision and disrespect — particularly the women who served as nurses, some of whom actually had decorations stripped from them because they weren’t men. They’ve told me about it for years, and I don’t understand, either. They won their war, only to come home and watch as the politicians threw away everything they’d accomplished.

Now, younger veterans who’ve returned from Iraq and Afghanistan have been telling me they don’t understand why people treat them like heroes.

That I do understand, at least from my perspective. They’ve done something for me that I wanted to do, but couldn’t because of an injury in high school. They helped preserve my country’s freedom. No matter where, when or how, every American who’s served with honor has done that.

My uncle never thought he was a hero, and neither does a friend of mine who was a Prisoner of War in Korea. When I interviewed a Medal of Honor recipient from the Vietnam War, he wanted to tell me about a village he helped to rebuild and the Viet Cong soldier he could have killed, but captured instead. They showed each other pictures of their families.

One of my friends said he was wearing an Army veteran’s cap when an Asian woman came up to him and asked, “You go Vietnam?” He said, “Yes, I did.” Then she told him she was Vietnamese and thanked him for what he and the others had done. “America now my home because of you,” she said.

“There are times when someone says, ‘Thanks’ in a way that makes a difference,” my friend said.

Hero-worship can ring hollow. Sincere gratitude, respect and support are what our veterans deserve, but don’t always receive. Understanding can come only from someone else who’s been there.

I asked an old friend ... one of the first men who told me about Vietnam ... why he thought there has been such a change in people’s attitude.

“It’s conscience,” he said. “Conscience because of the way they treated us and the guys who came home from Korea.” Korean War veterans, who were perceived as having played to a tie, were basically ignored.

During my two visits to the Korean War Veterans Memorial in Washington, I saw numerous people who were Asian in appearance. Many of them must have been South Koreans who remember that Americans saved their nation’s freedom more than half a century ago and have been helping to maintain it ever since.

Our veterans of Korea and Vietnam have provided the rest of us a great lesson: Regardless of how we may feel about the conflicts in which they serve, we should never again look down upon, or turn our backs against, those who offer their lives in our defense. It is to their credit that so many of them never stopped loving America and working to improve it.

The cost of freedom cannot be fully understood by those who haven’t had to bear it, either in person or through a loved one who came home damaged ... or not at all.

I didn’t have to pay that cost myself, but I can recognize it when I see it and hear it. It’s in the eyes and the voices of those who have paid ... and so is the pride they deserve to feel.

Tuesday is Veterans Day. When you meet our veterans, or those who are serving on active duty, please thank them for your freedom and tell them, Welcome Home.