SEOUL • Like many in North Korea's army of 1.2 million, Mr 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 Mr Eom, who served 10 years in the army before defecting to the South in 2010, a year before Mr Kim Jong Un assumed power in isolated North Korea.
The young leader has since expanded the use of so-called"soldier-builders", fuelling a construction boom as many of North Korea's Soviet-era conventional weapons become outmoded.
His military focus is increasingly on boosting "asymmetric"capabilities such as nuclear weapons, ballistic missiles and cyber warfare to deter North Korea's main enemies, the United States and South Korea.
Tensions with both have been on the rise since the start of the year.
North Korea - under tightened United Nations sanctions following its fourth nuclear test in January and a space rocket launch the month after - said on Monday that it would make a "physical response" to moves by the US and South Korea to deploy an advanced missile defence system on the Korean peninsula.
North Korea also said on Monday that it was cutting off its only channel of communications with Washington following a US decision to sanction Mr Kim by name for human rights abuses and to base a Terminal High Altitude Area Defence (Thaad) anti-missile system in South Korea.
North Korea is believed to have amassed enough plutonium for as many as 21 nuclear weapons, according to the Washington- based Institute for Science and International Security, and has been accelerating testing of various types of ballistic missiles, all in violation of United Nations Security Council resolutions.
The North is ramping up its cyber warfare capability as well, according to Seoul. Along with nuclear weapons and missiles, cyber warfare is now one of the North's "omnipotent swords", Mr Kim said, according to South Korea's National Intelligence Service.
The focus on asymmetric capabilities has been accompanied by a downscaling of the importance of the military within North Korea's power structure.
Slowly, Mr Kim is dismantling the "military first" policy of his late father Kim Jong Il and giving precedence to the ruling Workers' Party.
The most recent indication came last month when the National Defence Commission - a military body promoted by Mr Kim's father as one of the highest decision-making institutions in government - was replaced by the civilian-heavy State Affairs Commission.
"The Korean People's Army (KPA) is undergoing actual modernisation. Kim Jong Un is cutting through some of the fiefdoms and patronage networks that had grown too powerful," said Mr Michael Madden, an expert on the North Korean leadership.
After Mr Kim came to power, one of his first purges saw the removal in 2012 of then KPA chief of staff Ri Yong Ho.
Since then, Mr Kim has chipped away at the standing of senior military officers in public.
In 2014, he made his admirals take part in a swimming competition on the beaches of his summer palace while he watched, according to state media.
That summer, his air force commanders were made to fly fighter jets as part of a military flying competition, and he instructed his generals to take part in a target shooting contest, state media said.
"Hacks and cronies are out in favour of professional military men," said Mr Madden, adding that such competitions could distinguish genuine officers from those who rose through corruption and patronage.