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Joint drills signal a turn in Northeast Asia

South Korea and Japan have held their first joint military drills in seven years, reviving a defence partnership interrupted by political disputes. Their latest live-fire exercise in waters around Jeju brought together the South Korean Navy, Japan’s Maritime Self-Defence Force and the United States Navy. It was a practical sign that governments once divided by history, trade barriers and security concerns are again working on shared military problems.

North Korea’s ballistic-missile programme is the immediate reason for the renewed contact. Tokyo has acquired Aegis-equipped destroyers, while Seoul maintains a military designed to deter a surprise attack. Working together lets the two countries test detection, communications and defence procedures without changing their respective defence policies.

For Australians, the development has direct relevance. Canberra cooperates with Tokyo and Seoul through the Quad, bilateral agreements and regional exercises, and Australian English keeps the ‘c’ in ‘defence’. The connection reaches beyond government: Australian fans know Japanese and Korean teams through soccer, basketball and baseball, while local defence planners watch how the two neighbours manage their own tensions.

What the joint exercise tested

The exercise in Jeju’s surrounding waters was more than a photo opportunity. South Korean and Japanese ships conducted live firing, worked through anti-submarine tactics and practised procedures for detecting and engaging threats. The value lay in shared operating habits: how ships report contacts, how weapons are used safely during live fire and how information moves when a situation changes.

The American naval presence made the event trilateral rather than bilateral. That matters because Washington has agreements with both East Asian partners and places a premium on interoperability with US units. For Seoul and Tokyo, the exercise offered a way to build confidence with Washington while reducing friction when separate national chains of command meet.

The drill did not create a new alliance or settle every dispute between Seoul and Tokyo. It did something more modest and more useful: it inserted military cooperation into a diplomatic reset, giving officials practical reasons to keep defence channels open when political disagreements return.

Why the seven-year gap mattered

The previous joint live-fire exercise around Jeju took place in 2018. Since then, relations were held back by arguments over Japan’s colonial legacy, its treatment of Korean women forced into military sexual slavery during the war, and economic pressure after Tokyo restricted South Korean access to semiconductor-making equipment.

Those disputes made security cooperation politically awkward, even as North Korean tests continued. Leaders of both countries have now placed greater weight on the shared risk posed by missiles and surveillance aircraft. Meetings between Seoul and Tokyo have produced commitments to resume drills, consider real-time tracking of North Korean launches and reduce economic friction.

The seven-year gap therefore reflects more than a pause in scheduling. It captures a period when defence links drifted as political trust deteriorated. Reversing that pattern is significant, although regular exercises alone cannot resolve historical grievances or settle differences between the two armed forces.

Defence priorities and regional balance

The renewed drills sit within a wider regional balance shaped by North Korea’s nuclear programme, China’s growing military power and Russia’s war against Ukraine. Japan is building a more capable force around its Aegis destroyers, while South Korea continues to strengthen missile defence and nuclear-powered submarines. Cooperation allows both to use their existing assets more effectively.

Missile defence is the clearest example. Japanese interceptors need reliable detection and targeting information, and South Korea operates radar and warning systems that can contribute to a shared picture. That is relevant to Australia, whose northern approaches and maritime routes sit within the same Indo-Pacific security environment.

Australia’s defence planners in Canberra already work with both countries, including through Talisman Spirit. Defence suppliers in Adelaide, Newcastle and Perth are watching a market in which Japanese and Korean shipbuilding, electronics and precision components carry considerable weight. The government’s emphasis on resilient supply chains makes dependable access to those capabilities a commercial issue as well as a security one.

Trade, currencies and Australian interests

Security has economic consequences, but they should not be exaggerated. Japan and South Korea are major sources of vehicles, machinery, electronics and chemicals in Australia, while Australian iron ore, coal and LNG travel to East Asian buyers. More stable relations can lower uncertainty around those trade and investment relationships; they do not set commodity prices or exchange rates.

Local consumers encounter the two economies in showrooms, where Toyota and Mazda sit alongside Hyundai and Kia, and in the price of imported parts. Australian companies also hold yen- and won-denominated contracts. A stronger or weaker Australian dollar changes the local cost of those purchases, while the Reserve Bank of Australia separately uses its cash rate to keep inflation within its target band and support employment.

That distinction between policy and market sentiment is visible well beyond East Asia. In Turkey, a record low for the lira after another central-bank rate cut showed how quickly investor confidence can change. For Australian investors, the parallel is not that a naval exercise will move interest rates directly, but that currency markets remain sensitive to policy credibility and geopolitical risk.

Signs that cooperation could endure

The clearest evidence that this is a lasting shift would be a regular programme of exercises, not another exceptional event. Maritime drills can establish shared procedures, but air defence, submarine operations and logistics expose problems that commanders must solve over time.

Useful operational indicators include:

Broader diplomatic and commercial indicators include:

For Canberra, the measure will be whether military contacts become routine without creating new diplomatic friction. The value of the Jeju exercise is that it turns a diplomatic reset into habits that can survive the next political disagreement.