South Korea is quietly upgrading its military hardware, acquiring new fighters and missiles, and weighing purchases of nuclear submarines, even as Seoul pursues a peace track with North Korea that has brought Pyongyang to direct talks with the U.S.
The moves reflect the country’s ambition to create a force able to fight with minimal outside help, and concerns that its U.S. ally may not be in South Korea forever—a point highlighted by President Donald Trump’s abrupt cancellation of future joint exercises and talk of bringing troops home.
The military upgrades are focused on the air force and navy, traditionally seen as serving a less critical purpose than the army, which would play the primary role in countering any North Korean land invasion. The North’s ground forces number more than a million men, with 7.62 million in reserves, according to Seoul’s Defense Ministry.
To extend its air superiority, South Korea is replacing its aging fleet of F-4 and F-5 fighters with Lockheed Martin F-35As—stealth aircraft capable of hitting strategic underground targets. Many of the F-4 and F-5s will remain in service, as Seoul must contend with a North Korean military whose 810 combat aircraft outnumber the South’s two-to-one.
The first of the 40 F-35As purchased in 2014 are due to arrive in March, a Defense Ministry spokeswoman said.
The aircraft’s stealth and ground-attack capabilities make it ideal for pre-emptive strikes against North Korean leadership targets and ballistic missiles in the first hours of a conflict, said Eric Gomez, a defense analyst at the Washington-based Cato Institute.
While the jets were ordered under the government of his conservative predecessor, President Moon Jae-in has pushed ahead with the purchases as the North’s nuclear threat has grown. Mr. Moon has pledged to implement a missile-defense system incorporating F-35As to hit North Korean missile-launch sites.
To complement the new fighters, Seoul officials have said they are looking to buy more German-made Taurus air-to-surface missiles that can hit North Korean targets from beyond the range of most of Pyongyang’s conventional antiaircraft defenses.
The military-hardware purchases are a delicate issue for the government. In driving a detente on the peninsula, Mr. Moon has sought to avoid provoking Pyongyang while pursuing talks aimed at increasing economic engagement.
In March, the South’s defense minister didn’t attend the rolling-out ceremony of its new F-35As at a Lockheed Martin production facility in Texas, in contrast with defense ministers of other allied nations in recent years.
Mr. Moon has another balancing act. In the U.S., Mr. Trump has railed against the costs of overseas military alliances; this week in Singapore, he complained that Seoul doesn’t contribute “100 percent” to the defense of the Korean Peninsula.
South Korean officials on Wednesday remained puzzled by Mr. Trump’s sudden cancellation of joint military exercises after his summit with North Korean leader Kim Jong Un.
A spokesman for Mr. Moon repeated that South Korea “feels the need to better understand the exact meaning of President Trump’s remarks.” Secretary of State Mike Pompeo arrived in South Korea on Wednesday for talks with the foreign ministers of Seoul and Tokyo.
Back in Washington, Mr. Trump tweeted Wednesday morning that the U.S. could save “a fortune” by ceasing the exercises, as long as the U.S. and North Korea were “negotiating in good faith.”
Meanwhile, Japanese Defense Minister Itsunori Onodera called for the U.S. to maintain its military presence in South Korea. “U.S.-South Korea exercises and the U.S. military presence in South Korea have an important role in the peace and security of East Asia,“ said Mr. Onodera. A foreign ministry spokeswoman said Japan expected a ”detailed briefing from the U.S. side” on what Mr. Trump meant.
Mr. Moon has sought to appease Mr. Trump by promising to buy more American arms, at the same time hedging against any drawdown of U.S. forces—a long-held fear of many in South Korea.
But the weapons upgrades haven’t gone unnoticed closer to home. As North-South relations were warming in March, North Korea’s state media published a commentary accusing Seoul of having ulterior motives and lashing out at “military warmongers” for their “North-targeted arms buildup.” The article singled out South Korea’s purchases of the F-35As and Taurus missiles.
The F-35As can hit North Korean radar bases, communication facilities and concealed artillery along the demilitarized zone, neutralizing some of Pyongyang’s first-strike capabilities, said Shin In-kyun, head of the Korea Defense Network, a defense consultancy in Seoul.
Japan, too, has been beefing up its military under Prime Minister Shinzo Abe, by investing in cruise missiles, buying at least 42 F-35A fighter jets and unifying the command of its army. Tokyo is studying whether it can convert a helicopter carrier into an aircraft carrier on which F-35B fighters could land. The ruling party has urged Japan to consider buying its own F-35Bs.
Government officials and analysts say these steps are aimed at boosting the U.S.-Japan military alliance, not replacing it. Japan wants to show that with extra hardware and more personnel trained in amphibious warfare, it can work closely with the U.S. Navy and Air Force in combating regional threats.
“Japan is building up its defense capability to keep the U.S. forces in Japan,” said Toshiyuki Ito, a retired vice admiral in Japan’s navy who is a professor at Kanazawa Institute of Technology.
Back in Seoul, the government has looked into acquiring nuclear submarines to counter North Korea’s submarine-launched ballistic-missile program, recently hiring Mr. Shin of the Korea Defense Network to investigate the feasibility. The country has about 10 diesel submarines, according to a defense white paper, which can stay underwater for about two weeks, compared with nuclear subs that can remain submerged for months.
South Korea’s navy has also shown interest in acquiring a light carrier, a ship that would be critical to defending maritime trade routes, said Kim Jin-hyung, a retired South Korean rear admiral. A Defense Ministry spokeswoman confirmed the navy’s interest, but said Seoul didn’t have official plans for such a purchase at the moment.