On any given day, office workers in Seoul’s financial district shuttle in and out of shiny high-rises that overlook the Han River. Shoppers wander through shops at one of the city’s newest department stores. Down the street, lawmakers debate bills at the National Assembly, and worshippers gather at the country’s largest church.

What few of these people may know is that, high above their heads, on the roof of one of Yeouido’s towering skyscrapers, ROK soldiers operating M61 Vulcan rotary cannons and surface-to-air guided weapons are likely monitoring the skies for North Korean threats.