Like many of the 1.2 million people serving in the army in North Korea, Eom Yeong Nam spent more time holding the wooden handle of a shovel than a Kalashnikov rifle during his years in the 501 Construction Brigade.

"Except for basic military training two to three months a year, we worked on building apartments or concrete structures for nine to 10 months," said Eom, who served 10 years in the army before defecting to the South in 2010, a year before Kim Jong Un assumed power in the isolated country.

The young leader has since expanded the use of "soldier-builders," fueling a construction boom as many of North Korea's Soviet-era conventional weapons become outmoded.