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Maria Siow

Japan’s defence minister is touring Southeast Asia this week with what analysts describe as a clear, if diplomatically understated, mission: turning Indonesia and the Philippines into harder targets for Chinese maritime ambition.
Shinjiro Koizumi landed in Jakarta on Monday to sign a defence cooperation pact with his Indonesian counterpart Sjafrie Sjamsoeddin, coming hot on the heels of Tokyo’s landmark decision to lift a decades-old ban on the export of lethal weapons last month.
He heads next to the Philippines, where Japanese forces are currently training alongside US troops in the annual Balikatan military exercise.
Japan’s policy reversal on arms exports now permits weapons transfers to 17 defence partners, in a substantial break from its post-World War II pacifist doctrine.
Empowering Southeast Asian states will raise their diplomatic bargaining power vis-a-vis China
Yoichiro Sato, security analyst
Observers say Koizumi’s itinerary leaves little ambiguity about whom the shift is designed to deter.
“Empowering Southeast Asian states will raise their diplomatic bargaining power vis-a-vis China in maritime disputes,” said Yoichiro Sato, a professor of security studies at Japan’s Ritsumeikan Asia Pacific University and nonresident research fellow at the Korea Institute for Maritime Strategy.
Sato said Tokyo’s empathy with “like-minded” Southeast Asian states facing maritime pressure from China had grown alongside the increase in so-called grey zone tactics – persistent patrols and maritime and airspace intrusions – around the disputed Diaoyu Islands, which Japan administers and calls the Senkakus.

Koizumi’s five-day tour comes as Southeast Asia finds itself increasingly squeezed between an assertive China and an erratic United States. Into that anxious middle ground, Japan is deliberately positioning itself as what analysts describe as a credible third option.
Alfin Febrian Basundoro, an international relations lecturer at Indonesia’s Airlangga University, said Southeast Asia was seeking “reliable partners” that could offer security assistance.
Japan, in turn, sought to become an “alternative security provider” for the region’s middle powers, he said.
The agreement Koizumi signed in Jakarta on Monday reportedly covers humanitarian assistance, disaster relief, joint exercises and maritime collaboration.
It also “opens up opportunities for cooperation in defence equipment and technology”, according to Indonesian defence ministry spokesman Rico Ricardo Sirait.

Analysts say that language almost certainly refers to Indonesia’s potential procurement of up to eight Mogami-class frigates for roughly US$2.2 billion or a fleet of second-hand Japanese submarines in deals still under negotiation.
Japan’s defence industrial base not only meets Nato standards but, according to Alfin it also aligns neatly with Indonesia’s strategic priority of modernising its military through partnerships with advanced nations.
Ahead of Koizumi’s visit, Japanese media reports appeared to confirm that Tokyo was weighing the transfer of decommissioned naval vessels such as destroyers and submarines to Southeast Asian states – repurposing defence hardware that would otherwise be mothballed or scrapped.
Insurance policies
While Indonesia is approaching Japan’s security embrace with characteristic strategic caution – driven more by a desire for autonomy than any explicit “anti-China positioning”, according to Alfin – the Philippines’ stance is more complex.
Defence research analyst V.K. Parada, who previously served with the Philippine Navy, told This Week in Asia that feasibility studies on transferring Abukuma-class destroyer escorts to the Southeast Asian nation had been under discussion since last year.
He added the Philippines was a likely recipient for Japan’s Soryu-class submarines, which are due for early decommissioning in the late 2020s.

“If so, it would allow Manila’s submarine ambitions – a project which has languished since 2019 due to budgetary limitations – to finally come to fruition,” said Parada, who also lectures at De La Salle-College of Saint Benilde in Manila.
Japanese shipbuilders such as Mitsubishi Heavy Industries could eventually become Manila’s preferred suppliers for its military modernisation programme once Japan’s domestic defence industry had fully pivoted towards exports, he said.
For the Philippines, second-hand Japanese hardware could help address gaping capability gaps. But Parada said it was “also an insurance policy against Chinese aggression”.
Risking friction
Though Beijing would be “disappointed”, its response to the recent Jakarta-Tokyo defence pact was likely to be measured, Alfin predicted, channelled through “diplomatic pressure” rather than open confrontation, given Indonesia’s carefully nonaligned framing.
On Monday, Koizumi cast the Jakarta pact in the careful language of multilateral reassurance, saying it would make “a contribution to peace and stability for the region as a whole” amid “an increasingly complex and tense international situation”.
Manila is a different matter, however.
As a state locked in active territorial disputes with China in the South China Sea, “the Philippines should expect friction with Beijing to increase” following the transfer of Japanese vessels that represented a “direct capability enhancement”, Alfin said.
Japan and the US have spent recent years heavily investing in Philippine military and coastguard capacity, cementing a trilateral security relationship that Beijing views with unease.
“The fact that both Japan and the Philippines have ongoing territorial disputes with China and are part of the US alliance network would mean that any form of defence cooperation would naturally generate criticism from Beijing,” Parada said.


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Japan offers Indonesia and the Philippines lethal muscle to counter China

Japan’s Defence Minister Shinjiro Koizumi and his Indonesian counterpart Sjafrie Sjamsoeddin inspect an honour guard before their meeting in Jakarta on Monday. Photo: EPA

Japan’s Defence Minister Shinjiro Koizumi (right) and his Indonesian counterpart Sjafrie Sjamsoeddin inspect an honour guard before their meeting in Jakarta on Monday. Photo: EPA

Indonesian Defence Minister Sjafrie Sjamsoeddin (second from right) greets Japan’s Shinjiro Koizumi (right) upon his arrival in Jakarta on Monday. Photo: EPA

A Japanese Mogami-class frigate seen in an undated handout photo released by the Australian military. Photo: Australian Defence Force/AFP

A Soryu-class diesel-electric submarine is seen in an undated handout photo released by Japan’s military. Photo: Japan Maritime Self-Defence Force/Reuters

Japan ditches decades of arm export curbs as US reliability wavers

Japanese Type 10 battle tanks operate during a military drill in Funabashi, east of Tokyo, in January. Photo: Reuters

A Japanese Maritime Self-Defence Force Mogami-class frigate sailing in an undisclosed location. Photo: Australian Defence Force / AFP

A concept model of the Global Combat Air Programme‘s fighter jet is displayed during a defence equipment fair in Chiba, east of Tokyo, Japan, in May 2025. Photo: Reuters

Japan remains most trusted power in Southeast Asia despite military build-up: survey

Japan’s National Defence Academy students participate in a parade in Yokosuka, Kanagawa prefecture on April 5. Photo: AFP

Japanese Prime Minister Sanae Takaichi speaks after an online meeting with Asian leaders on Wednesday. Takaichi is pushing to amend the country’s pacifist constitution. Photo: Kyodo

Type 10 tanks operated by Japanese Ground Self-Defence Force troops at an exercise in Funabashi, Japan, in January. Photo: Reuters

How the Philippines became Japan’s closest security partner in Southeast Asia

A sailor raises the Japan Maritime Self-Defence Force ensign on board the JS Ise helicopter destroyer as it docks in Manila last year. Photo: AFP

A Japanese Type 12 surface-to-ship missile launched at a weapons range near Jervis Bay, Australia, last year. Japan is set to export lethal weapons after removing its long-standing curbs on arms exports. Photo: AP

Military officers from Japan greet each other during the opening ceremonies of the Philippines-US Exercise Balikatan at a military camp in Quezon City, Metro Manila, on Monday. Photo: EPA

The Philippines and the US hold a ceremony in Manila on Monday to begin their Balikatan joint military exercise. Photo: Kyodo

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Frigate and submarine sales are reportedly on the cards as Tokyo’s defence minister tours the region


Frigate and submarine sales are reportedly on the cards as Tokyo’s defence minister tours the region.


Japan offers Indonesia and the Philippines lethal muscle to counter China

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Frigate and submarine sales are reportedly on the cards as Tokyo’s defence minister tours the region

Frigate and submarine sales are reportedly on the cards as Tokyo’s defence minister tours the region