In April, South Korean troops fired warning shots to repel about 10 North Korean soldiers who briefly crossed the military demarcation line. The South’s military said the soldiers returned to North Korean territory without incident and that the North didn’t return fire.

The South’s Joint Chiefs of Staff said the military identified and tracked the individual near the central-west section of the military demarcation line and conducted a “guiding operation” before taking the person into custody Thursday night.

The division of Korea into North and South is the result of deep historical, political, and ideological conflicts that emerged in the aftermath of World War II. For over a thousand years, Korea was a unified nation.