North Korea’s claim that small South Korean drones have crossed into its airspace multiple times in recent months triggered speculation about who was behind the intrusion, with Seoul denying responsibility and ordering an investigation.

But now that a civilian has claimed he sent the drone, attention has begun to shift to another question: why the ROK military failed to intercept the unmanned aerial vehicle in the first place.

Pyongyang claimed on Jan. 10 that ROK drones attempted to surveil sensitive sites inside the DPRK on two occasions, Sept. 27 and Jan. 4. State media released images and reputed flight logs identifying a daytime launch from near Ganghwa Island, heading north toward Kaesong.

On Tuesday, South Korean President Lee Jae Myung questioned how the apparent civilian drones crossed through restricted airspace near the border without attracting the military’s notice, a fact that suggests surveillance gaps despite a sustained push to deploy new anti-drone assets following past intrusions.

Experts told NK News that the latest incident points less to operational failure than to structural limits in ROK air surveillance, which remains focused on countering drones coming from the North rather than those heading in the opposite direction.

And while there are steps Seoul can take to prevent a recurrence, they emphasized that there is no way to completely eliminate the emerging risks posed by small civilian drones.

ANTI-DRONE WEAK SPOTS

The ROK’s border area is covered by multiple layers of military sensors, including short-range air defense systems, low-altitude surveillance radars and counter-infiltration assets. It also lies within P-518 restricted airspace, where civilian drone operations are prohibited without authorization.

But if North Korea’s account is accurate, the alleged drones transited this airspace near the demilitarized zone (DMZ) without triggering an ROK military response to intercept them. This has raised the question of whether South Korea even detected the civilian UAVs.

The military’s apparent failure has drawn comparison to its response to North Korea’s drone incursions in Dec. 2022, when it was unable to intercept five UAVs that crossed into ROK airspace, including one that entered a no-fly zone over the presidential compound in Seoul.

But Shin Seung-ki, a research fellow at the Korea Institute for Defense Analyses (KIDA), warned that the two cases are not directly comparable. 

The Dec. 2022 incident, he said, involved multiple drones entering South Korean territory and flying over populated areas — a scenario squarely within the military’s defensive mission. The current allegations involve a single, smaller drone moving from south to north at a time, potentially exploiting areas where surveillance coverage is thinner or alert thresholds are higher.

“In this case, the alleged object did not enter our territory,” Shin said. “It moved in the opposite direction, where detection and response priorities are different.”

That does not mean such flights are irrelevant, the expert explained. Rather, it highlights a doctrinal choice about what the system is designed to catch first.

After the Dec. 2022 incident, Seoul established a Drone Operations Command to improve early warning and tracking. It also expanded deployment of tactical radars such as the TPS-880K and introduced portable jamming devices, or “anti-drone guns.” 

By 2024, South Korea fielded dozens of integrated anti-drone systems across capital region airbases and key command facilities. These combine radar, electro-optical, infrared sensors and radio frequency jammers into a single detection-and-response console.

Yet those upgrades did not fundamentally alter the orientation of South Korea’s air defense posture. Forward-deployed short-range radars are designed to detect north-to-south incursions, meaning small objects traveling in the opposite direction can be deprioritized within the sensor and command-and-control chain.

CHALLENGES IN DETECTION

Experts further emphasized the inherent difficulty of detecting small drones, regardless of which way they fly.

Imagery released by North Korean state media suggests the alleged drone was a lightweight fixed-wing platform with a wingspan of about 2 meters, likely built from materials that reduce radar visibility.

Jang Beong-chul, vice chair of the Korea Anti-Drone Industry Association, said drones of that size often fall below the discrimination threshold of conventional air defense radars and must instead be detected by specialized short-range, low-altitude systems.

“It’s even smaller than the North Korean drones we’ve seen in the past,” he said. 

The expert estimated that the drone’s radar cross-section could be well below 0.03 square meters. “Even if it crossed [military radar], it could easily fall below what existing systems are able to see.”

Post-incident analysis of radar data, radio-frequency sensors and system logs should clarify whether the object was detected but filtered out, or not detected at all, he said.

Shin of KIDA noted that environmental clutter also complicates detection, as small drones can resemble birds or other natural objects on radar, particularly in certain weather or seasonal conditions.

“At that size, if it mixes with a flock of birds, it becomes extremely difficult to distinguish,” Shin said.

In 2019, a KF-16 was scrambled to investigate a flock of geese. A day after the North Korean drone incursions in Dec. 2022, radar signatures thought to be hostile drones were later identified as migratory birds.

Shin said that while technologies to distinguish drones from birds are improving, achieving comprehensive coverage would require radars emitting enormous amounts of energy along the entire border — an approach that is “neither cost-effective nor operationally realistic.”

Yang Uk, a military analyst at the Asan Institute for Policy Studies, similarly assessed that the  latest incident reflects structural limits rather than a clear operational lapse.

He emphasized that counter-drone systems are designed primarily to detect coordinated or massed threats, such as swarm attacks.

“Detecting and intercepting a single drone that slips through unexpectedly is extremely difficult,” Yang said. “That is the reality under current system designs.”

ACCOUNTABILITY AND ADAPTATION

North Korea’s allegations have intensified scrutiny over whether South Korea’s surveillance doctrine reflects the emerging security environment, where civilian drones are widely accessible.

Despite the difficulties of detecting and defending against drones, experts said there are still steps Seoul can take to prevent a repeat of the latest incident.

Shin of KIDA told NK News that the military will need to move beyond its reliance on single platforms and adopt layered, overlapping surveillance supported by fully integrated command-and-control systems.

“Strengthening joint operations across services is essential to closing gaps exposed by small, low-flying aerial threats,” he stressed.

South Korea has begun exploring ways to complement ground-based sensors with airborne surveillance. Medium-altitude unmanned aerial vehicles developed domestically are entering production, with plans to equip them with sensors capable of monitoring ground activity and low-altitude airspace.

But technical upgrades alone will not resolve deeper structural limits. Local media have pointed to divisions in the military’s surveillance architecture, which is segmented by altitude. Under the current system, the air force is responsible for high-altitude monitoring, while the army oversees low-altitude airspace.

Shin said the split could complicate real-time information sharing and slow joint responses, particularly during ambiguous peacetime incidents.

“Information sharing among the military, police, local governments and aviation authorities is necessary,” he said. “That would determine how to respond, at what level and with what means.”

The challenge becomes more acute in wartime, he added, when large numbers of targets of varying sizes and speeds must be detected and distributed across command networks. 

“If we integrated and managed those systems comprehensively even in peacetime, response speed and capability could improve,” Shin said.

Rather than pursuing perfect coverage, Yang said a more realistic objective is incremental improvement — expanding sensor overlap, refining prioritization logic and strengthening inter-agency coordination.

But experts stressed that blind spots will persist under any system.

“There is no country that can detect every drone without exception,” Yang said.

Edited by Bryan Betts