For immediate help if you are in a crisis, call the toll-free National Suicide Prevention Lifeline at 1-800-273-TALK (8255), available 24 hours a day, seven days a week. All calls are confidential.

Canandaigua, New York — The Departments of Defense and Veterans Affairs are holding a conference in Nashville this week aimed at preventing suicides. A hotline launched in 2007 has answered more than 3.5 million calls, sending emergency help to nearly 100,000 people.

At the Veterans Crisis Line in Canandaigua, New York, the calls come in all day and night. Every day, 1,700 calls come in from veterans on the brink. CBS News was given rare access to the Veterans Affairs responders and their life-saving conversations.

Twenty veterans take their lives every day in America, or 6,000 a year. Personal finances, broken relationships and loneliness are all factors.

Responder Terrence Davis, a Navy veteran himself, said he always tries to answer by the second ring.

"It's highly stressful. Just knowing that you have someone else's life in your hands," Davis said.

Former Sergeant Danny O'Neel knows that feeling. Santa Cruz, California, may be a long way from the battlefield, but for him and his men, Sadr City, Iraq, is close by.

"It was hell on Earth. It was the most dangerous place at the time," O'Neel said.

In 2006, his unit lost nine men in the fighting. But back home, 14 have died at their own hands.

"The guys started isolating and drinking and doing things that they thought were helping them cope. And it, and it led to depression and suicide," he said.

O'Neel, who attempted suicide in 2012, today describes it as the new enemy with isolation as its accomplice. It's why he now arranges surfing reunions for his fellow warriors.

"When we're together, we feel that sense of family, that sense of a team that we miss," O'Neel said. "I've heard that the Pacific has no memory. For me, that's powerful because I can take Iraq out there and I can give it to the ocean. And I don't have to carry it around anymore."

Back in New York, the VA's responders are also trying to lift that burden — one call at a time.