An unidentified North Korean man crossed the heavily fortified land border separating the two Koreas and is in South Korean custody, the South’s military said Friday. 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 Joint Chiefs said it notified the U.S.-led United Nations Command about the incident and had not detected any immediate signs of unusual military activity by the North.