Present life: Rooney is the CEO of Cignal Global Communications Inc., a three-year-old telecom company that has attracted $54 million in investments. The company, based in Cambridge, Mass., projects it will reach $25 million in revenues this fiscal year. Its offices house the guts of a high-speed data network, as well as a recruit-inspiring indoor basketball court with the company's logo painted on the hardwood floor.

Former life: Rooney joined the U.S. Marine Corps in 1961 and served until 1983. One of his first assignments was training and evaluating officer candidates at Quantico, Va. He later served two tours of duty in Vietnam. "The situation in Vietnam in 1965 was one in which the United States first recognized or acknowledged that we needed to have a significant presence in the countryside," he recalls.

Lessons learned: Rooney says the best thing the Marine Corps taught him was to train, motivate, and, above all, trust young people.

At Quantico he learned the importance of teaching by example. "You are constantly being observed by the young men you are evaluating," Rooney says. "The first thing you learn is that those 50 eyes are on you virtually all the time. You must set the example in every way -- in the way you deal with people, in the way you carry yourself, in the way you assess situations, and in the way you look after the team."

It was in Vietnam that Rooney learned to trust the very young men under his command. That experience helped at Cignal, since its cofounders -- who hired Rooney and work closely with him -- are 24 and 23. Does Rooney believe that Gen X hotshots are difficult to work with? "They are no different from the thousands of young men I worked with in the Marine Corps," he says. "I find working with young people as wonderful today as in 1963. Youth is in the eye of the beholder. There are some very mature young men and women who are 20 years old. And they don't have habits that need to be changed. A poorly trained, poorly disciplined person at the age of 45 is harder to teach than a young person just out of a university. Young people are more willing to embrace change."

One final bit of Marine Corps wisdom: the value of documentation. "One of the first things they do at Officer Candidate School is give you a little notebook with a green cover," Rooney says. "It's about three inches by five inches, and you carry it in the breast pocket of your jacket. When anybody speaks to you, you write it down. That way, you can never say, 'Lieutenant, I forgot!"