How Japan, South Korea are building up naval capabilities for China threat

Japan's concept of the Aegis System Equipped Vessel (Japan Ministry of Defense)

SINGAPORE — As China dwarfs other Pacific nations with its naval expansion in terms of raw tonnage, number of hulls and the amount of capabilities hitting the sea, US allies Japan and South Korea are scrambling to modernize their own naval capabilities.

The scale of China’s naval expansion is stark. According to the BBC, citing a CSIS report , China’s four major shipyards produced 39 warships with a total displacement of 550,000 tonnes between 2019 and 2023. That same BBC piece also added that as of 2024 the People’s Liberation Army Navy (PLAN) had 332 warships to the US Navy’s 319.

Adding to the pressure for more naval capabilities is the dependence of East Asia’s economies on seaborne trade, meaning nations need a bolstered navy to protect incoming shipments.

In addition to China’s growing threat, both US allies also have to also contend with nuclear-armed North Korea’s missile programs as well as its own naval ambitions that has seen the Stalinist regime pursue its own nuclear-powered submarine .

So, in the race to modernize, what are Japan and South Korea doing?

Japan Increases Ballistic Missile Defense

Japan has stepped up defense spending over the past decade as both China’s and North Korea’s capabilities advance, with the country having allocated record defense budgets every year over the past decade, based on its budget documents .

The most significant naval shipbuilding program in Japan is for a pair of Aegis System Equipped Vessels (ASEV) sea-based Ballistic Missile Defense (BMD) platforms for the Japan Maritime Self-Defense Force (JMSDF) and will be used together with its other Aegis-equipped destroyers for protecting Japan’s airspace, according to Japan’s Ministry of Defense (MoD).

Japan had embarked on the ASEV program in 2020 following the cancellation of an attempt to introduce the Aegis Ashore system.

The ships will each displace approximately 14,000 tons and will be equipped with the Lockheed-Martin SPY-7(V)1 multi-function radar as its primary sensor for 128 Mk.41 Vertical Launch System (VLS) cells for SM-2, SM-3, SM-6 air-and-missile defense interceptors or Type 12 anti-ship missiles as well as Tomahawk cruise missiles, according to Naval News.

Construction of both ships is underway with the first ship being built by Mitsubishi Heavy Industries and the second by Japan Marine United. The ASEVs are due to be commissioned in early 2028 and 2029 , the MoD said.

Japan has also been steadily introducing new submarines into the JMSDF to replace the older Oyashio-class, commissioning one Taigei-class boat per year since 2022.

Japan’s other major naval program is the conversion of two Izumo-class Helicopter-Destroyers into aircraft carriers for the Lockheed-Martin F-35B Short Take off and Vertical Landing (STOVL) variant of the Lightning II stealth fighter.

Izumo and sister ship Kaga will receive a squared off flight deck along with other modifications to operate the F-35B, including the addition of a coating at the rear of its flight deck to enable it to withstand the heat from the STOVL jet’s exhaust gases during landing operations.

Conversion of the Izumo began in 2020 and is expected to be completed later this year or early 2027, while Kaga is expected to be completed in Japan’s fiscal 2027, beginning April 1.

In addition to these major programs, Japan is also continuing its build of the Mogami-class frigate for the JMSDF, with the introduction of the Improved Mogami design that has also been chosen by Australia and is in the running for New Zealand ’s frigate program, with the latter’s defense minister announcing the competition in May.

Japan is also introducing the Sakura-class Offshore Patrol Vessels into service from March 2027 and its recent defense budget request included seeking funding for unmanned transport vessels for moving troops and equipment from mainland Japan and the main island of Okinawa to its small outlying islands in the East China Sea, per the budget request.

South Korea’s Plans To Join Nuclear Sub Club

Like Japan, South Korea has a robust shipbuilding industry that has been vital to transforming it into a regional naval power alongside a defense industry that has gone from strength to strength, enabling it to indigenize an increasing portion of its armed forces.

The country recently saw the fulfillment of a long-time wish when US President Donald Trump agreed in May to allow South Korea to develop its own nuclear powered submarines .

South Korea’s defense establishment sees the introduction of nuclear-powered attack submarines as having taken on an increased importance as its northern neighbor steps up the development of its own nuclear submarine program to carry its submarine-launched ballistic missiles.

The South Korean nuclear-powered attack submarines will also have greater endurance than their diesel-electric counterparts, enabling them to stay out at sea for longer periods of time and allow them not just to stalk North Korean ballistic missile submarines but also allow them to rapidly respond to any land-based North Korean missile launches, according to research fellow at the Korea Institute of Defense Analyses Yu Ji-hoon during an interview on South Korea’s Arirang News.

The US ally is also pursuing a new class of 7,000-ton class destroyers that it is seeking to be equipped primarily with indigenous systems such as its own integrated sensor suite, combat management system, VLS and missiles, although the ships will still be powered by the GE Aerospace LM2500+G4 marine gas turbine engine.

Hanwha Ocean will be responsible for the design and construction of the first KDDX, which is expected to enter service in 2032. The company has also been tapped to supply a frigate to Thailand, with the Southeast Asian country announcing on Monday that the Korean shipbuilder has won a competition against rival South Korean shipbuilder Hyundai and Singaporean, Turkish shipyards for the contract, with the Thai government set to announce further details later in September.

日本的宙斯盾系统装备舰艇概念（日本防卫省）

新加坡——随着中国海军在吨位、舰艇数量和出海作战能力方面遥遥领先于其他太平洋国家，美国的盟友日本和韩国正争先恐后地对其海军能力进行现代化改造。

中国海军扩张的规模令人瞩目。据英国广播公司（BBC）援引战略与国际研究中心（CSIS）的报告称，2019年至2023年间，中国四大造船厂共建造了39艘军舰，总排水量达55万吨。BBC的同一篇报道还指出，截至2024年，中国人民解放军海军（PLAN）拥有332艘军舰，而美国海军则拥有319艘。

东亚各国经济对海上贸易的依赖，进一步加剧了对海军能力的需求，这意味着各国需要加强海军力量来保护入境货物。

除了中国日益增长的威胁之外，美国的两个盟友还必须应对拥有核武器的朝鲜的导弹计划，以及朝鲜自身的海军野心，这个斯大林主义政权一直在寻求建造自己的核动力潜艇。

那么，在现代化竞赛中，日本和韩国都在做什么呢？

日本加强弹道导弹防御

过去十年，随着中国和朝鲜的军事能力不断提升，日本加大了国防开支。根据日本的预算文件显示，过去十年，日本每年都拨出创纪录的国防预算。

据日本防卫省称，日本最重要的海军造船计划是为日本海上自卫队建造两艘配备宙斯盾系统的舰艇（ASEV），作为海基弹道导弹防御（BMD）平台，这两艘舰艇将与日本其他配备宙斯盾系统的驱逐舰一起用于保护日本的领空。

日本在 2020 年取消了引进陆基宙斯盾系统的尝试后，启动了 ASEV 计划。

据海军新闻报道，这些舰艇每艘排水量约为 14,000 吨，并将配备洛克希德·马丁 SPY-7(V)1 多功能雷达作为其主要传感器，用于 128 个 Mk.41 垂直发射系统 (VLS) 单元，以发射 SM-2、SM-3、SM-6 防空导弹拦截器或 12 型反舰导弹以及战斧巡航导弹。

两艘舰艇的建造工作正在进行中，第一艘由三菱重工建造，第二艘由日本海上联合公司建造。防卫省表示，这两艘海上支援舰艇预计将分别于2028年初和2029年初服役。

日本也一直在稳步地向海上自卫队引进新型潜艇，以取代老旧的亲潮级潜艇，自 2022 年以来每年都服役一艘大鲸级潜艇。

日本的另一项重大海军计划是将两艘出云级直升机驱逐舰改装成航空母舰，用于搭载洛克希德·马丁公司生产的F-35B闪电II型隐形战斗机的短距起飞和垂直降落（STOVL）版本。

出云号及其姊妹舰加贺号将进行方形飞行甲板以及其他改装，以便操作 F-35B 战斗机，包括在飞行甲板后部增加涂层，使其能够承受短距起降战斗机在着陆作业期间尾气的热量。

出云号的改装工作于 2020 年开始，预计将于今年晚些时候或 2027 年初完成；而加贺号的改装工作预计将于日本 2027 财年（从 4 月 1 日开始）完成。

除了这些重大项目外，日本还在继续为日本海上自卫队建造最上级护卫舰，并推出了改进型最上级设计。该设计也被澳大利亚选中，并且正在参与新西兰护卫舰项目的竞标，新西兰国防部长于 5 月宣布了这项竞争。

日本还将从 2027 年 3 月起引进樱花级近海巡逻舰，并且根据预算申请，其最近的国防预算申请包括寻求资金，用于建造无人运输船，以便将部队和装备从日本本土和冲绳本岛运送到东海的离岛。

韩国加入核潜艇俱乐部的计划

与日本一样，韩国拥有强大的造船业，这对于将其转变为地区海军强国至关重要；此外，韩国的国防工业也日益强大，使其能够实现越来越多的武装部队国产化。

韩国最近实现了长久以来的愿望，美国总统唐纳德·特朗普于5月同意允许韩国发展自己的核动力潜艇。

随着韩国北方邻国加紧发展自己的核潜艇计划以携带潜射弹道导弹，韩国国防机构认为引进核动力攻击潜艇的重要性日益凸显。

据韩国国防分析研究所研究员俞智勋在接受韩国阿里郎新闻采访时表示，韩国核动力攻击潜艇的续航能力也将比柴电潜艇更强，使其能够在海上停留更长时间，不仅可以跟踪朝鲜弹道导弹潜艇，还可以对朝鲜任何陆基导弹发射做出快速反应。

美国的盟友也在寻求建造一种新型的7000吨级驱逐舰，并希望主要配备国产系统，例如其自身的集成传感器套件、作战管理系统、垂直发射系统和导弹，尽管这些舰艇仍将采用通用电气航空航天公司的LM2500+G4船用燃气轮机发动机提供动力。

韩华海洋将负责首艘KDDX的设计和建造，预计将于2032年投入使用。该公司还被选中向泰国提供一艘护卫舰。泰国政府周一宣布，这家韩国造船企业在与韩国现代造船、新加坡和土耳其的造船厂的竞争中胜出，赢得了这份合同。泰国政府将于9月下旬公布更多细节。