North Korea‘s military provocation seems to be going to the extreme. It fired 25 missiles, including short-range ballistic missiles, into the East and West Seas on Wednesday. One of the ballistic missiles flew across the Northern Limit Line, a de facto maritime border, with South Korea.

It is reportedly the first time since the division of the Korean Peninsula into the communist North and capitalist South in 1945 that a North Korean ballistic missile landed south of the borderline. Its military provocation seems to be getting more aggressive and fiercer.

The missile fell in international waters, but it was very close to South Korean territory. It landed just 57 kilometers from Sokcho, Gangwon Province. An air raid alert was issued for Ulleung Island in the East Sea. North Korea effectively trespassed into South Korea, though the missile landed in international waters. This cannot be viewed as anything but intentional. It is concerning that Pyongyang seems to be baring its intention to turn the Korean Peninsula into a stage for armed collision. A stern response is required.

South Korea‘s swift tit-for-tat was a proper response. Its fighter jets fired three air-to-surface missiles into high seas north of the NLL. The missiles landed in an area north of the line at a distance almost equivalent to that of the North’s missile that dropped south of the maritime border. This shows the South‘s ability and preparedness to respond firmly and strike with precision.

The North seems to be using the ongoing combined air drills of South Korea and the United States as a pretext for its latest provocation.

The “Vigilant Storm” exercise which kicked off on Oct. 31 is underway across the skies of the Korean Peninsula. More than 240 aircraft including advanced stealth jets F-35A and F-35B are mobilized in the drill.

Earlier Wednesday, Pak Jong-chon, secretary of the Central Committee of North Korea‘s ruling Workers Party, warned that South Korea and the US will pay a “terrible” price if they use force on North Korea. Park argued that the US-South Korea combined air drills are a military exercise to invade the North. This argument is a pretext to shift responsibility to South Korea and the US and carry out military provocations. After the warning, the North fired missiles followed by about 100 artillery shells.

It is not easy to predict how far the North‘s provocation will go. North Korea is expected to continue provocations at least until the Vigilant Storm ends. The US and South Korea agreed to extend the five-day drill in response to North Korea's recent provocations. On Thursday morning, it fired an intercontinental ballistic missile and two short-range ballistic missiles into the East Sea.

It is still valid to expect the North‘s seventh nuclear test. It will likely keep raising military tensions until the test.

It is hard to exclude the possibility of Pyongyang trying to incapacitate the NLL. A North Korean merchant ship crossed the line in the West Sea on Oct. 24, then retreated northward as a South Korean naval convoy fired warning shots. Afterwards, the North fired 10 artillery shells into the western sea from rocket launchers. It is likely that the North Korean ship crossed the line intentionally.

The North also flew over 150 warplanes in airstrike drills on Oct. 10, while criticizing a US aircraft carrier for re-entering waters near the peninsula to join South Korea-US naval drills. It once fired a submarine-launched ballistic missile from a reservoir.

North Korea will not stop its provocations. It is apparently raising the level of provocations because it is counting on the nuclear bombs it is developing. South Korea must respond on the assumption that the North will escalate provocations.

Obviously what Pyongyang aims for from its provocations is to halt the South Korea-US combined exercises and shake the alliance. However, the South must not succumb, and respond sternly. It should beef up its combined drills with the US and show the alliance’s overwhelming power. Seoul and Washington must seek a solution to deter the North‘s increasingly rough provocations structurally.