Daniel Flynn could be at his job as a cancer specialist at Caritas Holy Family Hospital in Methuen or spending time with his four children. Instead, he's wearing 50 pounds of body armor in the 120-degree Iraqi heat.

Flynn, a 62-year-old colonel, delayed his retirement from the Army Reserve to spend three months in Camp Bucca in the southern part of Iraq, home to the largest prison in that country. He works as a general medical doctor, treating detainees at the U.S.-run facility. He also treats soldiers and serves as a backup for mass casualty incidents.

It's not the first time he's been in a war zone.

He joined the Army in 1967 when he was 22 years old, and survived a year in Vietnam.

"Number one, you're serving your country," he said during a telephone interview this week. "And number two, there's a humanitarian part of this whole thing. There's a lot of extra care given to detainees that I don't know if you would see in other countries."

Flynn, a former North Andover resident who now lives in Wakefield, has been in Iraq since May. Many of the prisoners he treats are suffering from diabetes, hypertension, allergies and asthma.

Many of the 20,000 detainees have never seen a doctor. Flynn doesn't let the thought that some of them may have been trying to hurt fellow Americans affect the way he cares for them.

"I treat them as if they could be innocent, and I don't judge them - that's my job," he said. "I would hope that if an American was captured, that the same thing would happen, that there would be some people on the other side that would do that."

He said the prisoners are treated well and given access to phones, television, medical and dental care, and visits with their families. They get to play soccer, and they even get paid, he said.

Flynn graduated from Northeastern University in 1969, while he was in the Army. He received an honorable discharge in 1970. He attained a master's degree from Harvard in 1972, and then his medical degree from Jefferson Medical College in 1978.

He joined the Army Medical Corps as a reservist in 1986 and has remained in it ever since. His service has brought him to different parts of Asia and Central America, and now to the Middle East.

He wanted to serve in Iraq because he spent years preparing to treat soldiers wounded in combat after he became a doctor.

"I was always training for war," he said. "When I saw I was retiring, I never actually applied all of the Army training that I got. This was a chance to finish off my Army career actually applying what I trained to do."

He put his skills to the test on June 9 when insurgents fired a rocket into the prison, killing eight prisoners and injuring 75 people.

He pulled shrapnel out of people's wounds and checked their airways.

"Ready to do an artificial airway in a neck if I had to," he said. "That's what I was trained to do - real combat medicine."

Flynn sees parallels between the wars in Vietnam and Iraq.

The public has grown tired of the war in Iraq, just like they did with Vietnam, and even World War II, he said.

"I think every single war, people are like that," he said.

There are other similarities, unfortunately, like the 122 mm rockets, which were used in Vietnam and are still being used in Iraq.

"It's like they're following me," he said.

Flynn's son, Connor, 19, a 2006 graduate of Phillips Academy in Andover, is attending the U.S. Naval Academy in Annapolis, Md. He will be a Marine and expects to eventually be deployed to Iraq.

"I really feel my father upholds the Army's values of duty, honor and country," Connor said. "I can only hope that I can be as good a man as he is one day. I love him very much."

Flynn is supposed to return home in October and is scheduled to head back to work at Caritas Holy Family Hospital on Nov 1.