One trained soldiers to use Stinger missiles to shoot down enemy jets and helicopters.
Another sailed silently beneath the seas in a submarine during the Cold War.
A third piloted Black Hawk helicopters in Iraq.
All three are now transferring their wartime skills to classrooms as teachers.
Along with thousands of other former members of the military, they're part of an effort to bolster America's teaching corps with worldly veterans whose leadership skills and life experiences could be valuable in the classroom.
Troops to Teachers, a nearly 20-year-old Pentagon program, has produced more than 15,000 teachers, largely for high-need schools. The program gives guidance about state teaching requirements and how to make the transition to teaching.
"A lot of times kids want to test me because I was in the military," said Anthony Kajencki, a West Point graduate and former air defense artillery officer who teaches at Northern High School in Durham, N.C. " 'Look at this guy. Let's see how tough he is. Let's see if I can push him.' "
Kajencki, who's 41 and is known to his students as "Capt. K," said one reason he chose to become a high school math teacher was a commitment he made after West Point to a lifetime of service. The military taught him about teamwork.
"I learned about how to be resilient and how to just take whatever West Point gave me and withstand it and continue on," he said. "We were constantly tested."
It's what he strives to pass on to his students; that and what it's like to jump out of a plane.
"Our people come with a background," said Ed Kringer, the director of the Voluntary Education Program, of which Troops to Teachers is part, at the Department of Defense. "They're disciplined. They have leadership skills. They have a lot to offer that can transfer into the classroom."
Congress has authorized about $8.5 million per year for one-time $10,000 bonuses for people in the program who agree to work in schools that primarily serve low-income, high-needs students.
Kajencki spent more than seven years in the Army, including stints at Fort Bragg in North Carolina and Fort Drum in New York, training soldiers to use missiles to take down enemy aircraft. He also was a protocol officer in Bosnia for a commanding general.
The all-boys class of fifth-graders in North Charleston, S.C., where John Helton, a 50-year-old retired Coast Guard commander, teaches loves to hear stories from his three-decade career: tales of rough seas, rescues at sea and Cold War-era submarines deep under the sea.
"That's how you get the buy-in," Helton said. "Kids nowadays don't want to hear a talking head. They want to hear someone who is excited about it and has something to say and really cares about them."
"If we can get ahold of the kids when they're young and make a difference in their lives and spark a desire to learn," he said, "then we'll have them for life."
Brandon Phillips' military career is also something he talks about occasionally in his fourth-grade class, especially when students are curious. He said he kept it light and nonspecific.
For example, when he teaches math to his fourth-graders in Springfield, Ga., he might say, "I had to know how to do that when we would fly missions in Iraq. Pilots need to know how to do this."