What dodging North Korean missiles taught me about shooting down Kim Jong Un's growing arsenal

• A North Korean missile launch in August 2017 sent people in South Korea and Japan scrambling to bunkers.
• The missile broke up and fell into the Pacific, but North Korea's growing missile arsenal remains a concern.
• The US, South Korea, and Japan all have missile defenses, but stopping an incoming missile is no easy feat.

As a South Korean military interpreter participating in a combined exercise with the US on August 29, 2017, my day began with a jolt, as a North Korean ballistic missile hurtled toward Japan at 6:00 a.m.

Not knowing the exact trajectory in the first few minutes, I quickly headed into underground bunkers near Seoul with my fellow service members.

Radars predicted that the missile would cross Japan's airspace over its northernmost island, Hokkaido. Japan was faced with two options: shoot it down or let it pass.

The Japanese government chose not to intercept that missile. It ultimately fractured into three pieces and landed in the Pacific Ocean, but debris could have fallen onto unsuspecting citizens. Even worse, an actual nuclear strike could wipe out an entire city.

With North Korea demonstrating its ability to reach most of the US, improving missile-defense systems has quickly become a concern for everyday citizens.

Tokyo's decision to disregard that ballistic missile compelled me to ask whether South Korea, Japan, and the US were well prepared for such missile threats.

Layered defenses, split-second decisions

The US defends its territory with a layered system that has several chances to intercept a North Korean missile: in the boost phase soon after launch near the Korean Peninsula and Japan, again over the ocean during the missile's midcourse phase, and lastly near US territory as the missile enters its terminal phase.

All three options, however, need much improvement.

An intercept over the ocean is challenging because Aegis ships and fighter jets must anticipate where it will impact, which is made more challenging by the fact that Aegis ships and fighters have never attempted to intercept a ballistic missile in combat.

For land-based defense, the Pentagon has slammed its own flagship system, the Ground-based Midcourse Defense, for its insufficient radars and unreliability: Its success rate is barely over 50%.

Improving the intercept ability of South Korea and Japan has therefore been important to the US's own national interests.

The US's recent termination of the missile guidelines it imposed on South Korea in 1979 is a step toward allowing its allies to prepare defenses for North Korea's long-range missiles.

With limits on the range and payload of its missiles now lifted, South Korea will be able to develop advanced missile-defense systems that could help deter long-range missile attacks.

My experience dodging North Korean missiles, however, highlights the need to review the intercept process further to reduce the risks posed by needing to make a split-second decision. Hesitance to shoot down missiles shows that technological ability does not necessarily equal safety.

Why did those countries decide not to respond during that August 2017 missile test? Within minutes of the launch, most countries could tell from radar tracking that the missile was headed toward the Pacific Ocean.

In the case of Japan, the government may have decided not to attempt to do so simply because it was an unnecessary risk. The missile appeared unlikely to harm civilians, and, more importantly, a failed attempt would send a catastrophic message that its US-backed missile system cannot stop North Korean missiles.

A second possibility, however, is that Japan's Aegis destroyers were unable to intercept the missile in the first place.

The North Korean missile reached an altitude of 550 km, higher than the 500-km range of the Aegis Standard Missile-3 (SM-3) interceptor. The Aegis interceptor may also have not been in the right place, as the missile passed over a region that is not a routine training area.

Why didn't South Korea try to shoot it down? South Korea's US-made Terminal High Altitude Defense (THAAD) system reports a 100% test rate, but it has never been used in combat.

THAAD is also designed to shoot down missiles as they re-enter the atmosphere during their terminal phase. The North Korean missile was only in range during its first two phases: boost and midcourse.

Military and diplomatic challenges

What can be done about future missile tests?

In order to shoot down a missile during its boost phase, a ship with an SM-3 would have to be right next to the launch site and intercept immediately upon launch.

As the US military has noted, boost-phase intercepts are quite unlikely due to the challenges in anticipating a launch and the decision process needed to approve such a response. For fighter jets to intercept a missile in that phase, the jets would need to be at a provocatively close distance to the launch site.

None of the missile defenses in Japan or South Korea - which include US-made Patriot missile systems - can intercept missiles during their midcourse phase.

South Korea could technically develop a midcourse defense in the future, but past pushback from China indicates there will be a substantial challenge to doing so. Seoul suffered as much as $7 billion in economic losses when China boycotted Korean products in response to the deployment of the THAAD system.

With nearly one-quarter of South Korea's exports and one-fifth of Japan's exports going to China, safely navigating the US-China rivalry while ensuring a defense against North Korean missiles will be a complex military and diplomatic task.

Jessup Jong is a Korean Army veteran (Intelligence Branch at the Transportation Command) and a master's student at Johns Hopkins University's School of Advanced International Studies. His latest book is "Human Suffering in North Korea."