These others were all new to Korea, such that I was leading them around. I translated the sign:
등산객 여러분의 안전을 위해 우회도로를 이용해 주시기 바랍니다
Shooting in Progress
Hikers are requested to use the bypass road for their own safety.
Commanding Officer, Unit 9100
We'd come down from summit on the right-hand-side path. At the time, I assumed that this side path would lead to a shooting range which would be blocked off by barbed wire or something. I was sure we wouldn't just walk into a place which had live bullets whizzing around.
Only one time have I heard gunfire in Korea. It was while hiking north of Ilsan in Paju County, which is adjacent to the DMZ. Paju's hiking trails are full of elaborate and well made but unoccupied defensive positions on hilltops, some small and some big enough for artillery, as well as networks of trenches, covered tunnels, dug-out hiding places big enough for vehicles or tanks, and other such things.