Loopholes have emerged in the military’s surveillance and vigilance of the Northern Limit Line(NLL) in the East Sea after four North Koreans crossed the de facto maritime border from the North to the South, undetected. 

A wooden fishing vessel carrying the North Koreans crossed the NLL and traveled to waters some eleven kilometers east of Sokcho, Gangwon Province around 7:10 a.m. Tuesday. The military failed to find the boat until a private vessel alerted authorities. 

An official of the Joint Chiefs of Staff(JCS) said the JCS launched an operation to track down the boat as a “suspicious vessel” around 5:30 a.m. after its radars and thermal observation devices spotted the boat. The official said the JCS sent a patrol aircraft and high-speed boat but failed to find the North Korean vessel until it was alerted by a private fishing boat. 

The Navy, on its part, has said that conducting surveillance on the NLL in the East Sea is difficult compared to watching the NLL in the Yellow Sea, also known as the West Sea. 

A Navy official said surveillance and vigilance of the NLL in the Yellow Sea is relatively facile given that the border is short and there are many islands, but that the NLL in the East Sea extends more than 400 kilometers long, making it difficult to spot small-sized wooden vessels far out at sea. 

Tuesday is not the first time the military failed to properly detect a North Korean fishing boat that crossed the NLL in the East Sea. 

The military had failed to spot a North Korean fishing vessel carrying four people on June 15, 2019 and a ship which was later discovered in waters off Gangneung, Gangwon Province on October 1, 2009.