The 15 male ballet students groaned as they strained to do the splits and laughed with relief after their teacher counted to five and let them relax.

Once a week, a group of soldiers from the Republic of Korea near the Demilitarized Zone that divides the Korean Peninsula trade army boots for ballet shoes in a class intended to ease the stress of guarding the world's most heavily fortified border.

"There's a lot of tension here since we live in the unit on the front line, which makes me feel insecure at times," said Kim Joo-hyeok, a 23-year-old sergeant doing his nearly two years of military service that is mandatory for ROK men.

"But through ballet, I am able to stay calm and find balance as well as build friendships with my fellow soldiers," said Kim, who is learning ballet for a second year and plans to continue when he is discharged from the army.

Wearing shorts and T-shirts along with their dancing slippers, members of the army's 25th Division are taught each week by a ballerina from the Korean National Ballet under a program that began last year and has already included a performance of Tchaikovsky's Swan Lake.

Most of the students at a recent session were first-timers.

"Being in the army itself can be difficult, so I wasn't sure what kind of help I can be here," said Lee Hyang-jo, a ballerina at the Korean National Ballet who visits the base once a week to train the soldiers.

"But as the soldiers learn ballet little by little, they laugh more and have a great time and seeing that makes me think that coming here is worthwhile," she said.

As the sun-tanned, crew-cut dancers practiced movements including the splay-kneed plie to classical music, outside the studio, another group of soldiers played soccer.

But ballet toughens you up too, said Lieutenant Colonel Heo Tae-sun.

"Ballet requires a great amount of physical strength and is very good for strengthening muscle, increasing flexibility, and correcting posture," Heo said.