A major communications breakdown between branches of the South Korean military hamstrung its response to a North Korean drone that entered Seoul airspace last month, the Joint Chiefs of Staff (JCS) told parliament on Thursday

JCS’ statement followed a weekslong investigation into the Dec. 26 incident, when the military failed to intercept or shoot down an unmanned aerial vehicle (UAV) that flew near the presidential office and four other North Korean drones near the western inter-Korean border.

At a parliamentary session on Thursday, JCS Chairman Kim Seung-kyum said the front-line unit that first detected the drone intrusion at 10:19 a.m.