SAN DIEGO – The sailor had been back from war for just over a year when friends invited him to watch an unusually emotional training exercise for troops preparing to deploy.

The drill happened not on a military base but at a film ­studio, where Marine and Navy medics role-played wartime rescue missions with actors who had, in real life, lost limbs in motorcycle or car crashes or to ailments such as cancer.

Those on hand weren't sure how Joel Booth would react. The 24-year-old had been attached to a Marine battalion in Afghanistan as a naval combat medic — until he stepped on an explosive device and doctors, two years ago, amputated his right leg below the knee. Since returning home he has had to learn to adapt while also ­coping with post-traumatic stress.

But Booth was transfixed as fake bombs exploded and medics practiced the type of rescue missions he'd once been on, saving the amputee actors — as he, in the end, had to be saved.

Then the young veteran did something unexpected: He asked for an audition.

Perhaps, he thought, this injury that had forever altered his life could help save someone else's. What he didn't know was how much reliving the horrors of war would help him, too.

A U.S. Navy corpsman pulled an actor to safety during “reality based training” in San Diego late last year.

"In society, amputees are seen by people on a large scale as having a disability, being weaker. But … even someone who doesn't have a hand can still operate a weapon to be able to defend themselves," he said.

"It's the same thing for me. I'm not afraid of it just because something bad happened. For people who haven't been in combat, it's hard to understand."

Producer Stu Segall started Strategic Operations in 2002 shortly after the start of the Iraq war to offer the military what it calls "hyper-realistic" training by using movie-making special effects and actors.

The group has since trained hundreds of thousands of troops in re-created scenes from Iraq, Afghanistan, Somalia and other hot spots. The creators strive to make the re-enactments as jarring as possible so troops experience war first in a controlled environment, and learn not to be rattled by it.

Marine Second Lt. Duane Blank, a commander who has gone through similar training, said amputee actors add a degree of realism that no one else can.

"The visual effect is invaluable because it's something you don't encounter every day," said Blank, an Iraq war veteran.