The Korea-US military alliance is showing signs of abnormality.

The US Marine Corps deployed 14 aircraft from Hawaii to the Korean Peninsula for training last month.

This came to light through a statement released by Lt. Gen. Lewis A. Craparotta, commander of the US Marine Forces Pacific, for a security seminar in Seoul on Tuesday. Military authorities in Seoul did not disclose the training.

The exercise was exceptional. The US Marine Corps usually dispatches aircraft to the Korean Peninsula from US bases on the Japanese island of Okinawa or its own territory of Guam. Military experts here regard the training as an effectively independent US Marine exercise.

The US has deployed EO-5C Crazy Hawk airborne reconnaissance aircraft over the West Sea and RC-135S Cobra Ball special reconnaissance aircraft to Okinawa since late March to track ballistic missiles from North Korea. It recently dispatched a US Coast Guard vessel with a mission to combat the North’s maritime sanctions evasion.

US President Donald Trump once said he would cancel military exercises between the US and South Korea because they were “tremendously expensive,” but now the US conducts effectively independent military training and activity at its own expense. Washington may be considering multiple objectives, but whatever its intentions are, such a move is undesirable for South Korea, as it could loosen its alliance with the US.

A military alliance between two states is a pledge to fight together if either side is attacked. To win a fight, they should train together and maintain combat readiness.

Yet South Korea and the US decided to abolish three major joint military drills. They agreed to do so to facilitate dialogue between the US and the North, but the North’s commitment to denuclearization has turned out to be unreliable, as shown by the Hanoi summit with the US that ended without a deal.

Dialogue is important, but it is questionable if talks with an untrustworthy communist state for the sake of talks will produce intended outcomes. Experts warn that Pyongyang appears to be repairing a rocket site and could soon conduct a launch.

In this situation, the defense readiness of the South is indispensable for its security. Suspended or abolished exercises should resume. However, the Moon Jae-in administration is moving in the opposite direction.

Korea and the US will reportedly scale down their combined air drills. It seems the Moon administration adamantly believes Pyongyang’s dubious promise to denuclearize, though the nuclear threat remains. The North showed its true colors at the Hanoi summit. It wants effectively complete sanctions relief in exchange for the partial dismantlement of its nuclear facilities.

Nonetheless the Moon administration appears to have little interest in being on its guard. It tries instead to avoid agitating Pyongyang. For a second year in a row, Moon did not attend a ceremony last month to commemorate South Korean victims of North Korea’s military provocations in the West Sea. Defense Minister Jeong Kyeong-doo called the provocations “disgraceful” incidents. Considering the case, the US military activity appears more natural.

Geopolitically, South Korea has to survive among powers seeking hegemony. Vague hopes for China to do something for the security of the Korean Peninsula turned out to be mere illusion. Beijing has stood by the North at every critical moment as its ally and lifeline. If Washington breaks away from Seoul, it would be hard to expect Japan to be an ally as strong and trustworthy as the US. The way to go for the South is self-evident.

Military allies should share important information and act together accordingly. The South Korean military authorities knew roughly the US Marine plan to deploy aircraft from Hawaii, but reportedly knew little about the details. If there are reasons one side should act alone, suspicions of a crack in the alliance become inevitable.

The Moon government has called the US alliance ironclad, but one cannot but wonder if South Korea has lost trust to the extent of prompting the US military to pass it over. Moon said some forces undermine the Korea-US alliance, but it is his obstinate policy to appease North Korea that has induced the current situation.