Japan's plan to join a United States-Philippine military drill is raising questions over how the Association of Southeast Asian Nations can safeguard its neutrality and preserve its centrality, analysts say.

They noted that ASEAN leaders may need to weigh the practical gains from Japanese defense cooperation against the political cost of normalizing the presence of a former occupying power, given lingering wartime memories in the region.

Japan will send about 1,400 Self-Defense Forces personnel to the Balikatan exercise in the Philippines from Monday to May 8, making it the third-largest contributor after the US and the Philippines. Troops from Australia, Canada, France and New Zealand will also take part.

Julia Roknifard, a senior lecturer at the School of Law and Governance at Taylor's University in Malaysia, said ASEAN states joining the exercise should make it clear that participation reflects security cooperation rather than political alignment, in line with the bloc's neutral stance.

She described such drills as a form of US security diplomacy, saying many countries take part not necessarily because they align politically with Washington but rather as part of broader cooperation.

However, Japan's involvement this year is a "highly provocative development", she said, citing moves by Prime Minister Sanae Takaichi, including remarks on China's Taiwan.

Hiroshi Shiratori, a professor of political science at Hosei University in Tokyo, said Japan's increasingly proactive defense posture may be perceived by its neighbors as a departure from its postwar identity as focusing on peace, diplomacy and dialogue.

If that perception becomes widespread, Japan itself could be viewed as a source of regional instability, he said.

Lucio Blanco Pitlo III, president of the Philippine Association for Chinese Studies, said ASEAN countries would likely welcome Japan as a defense partner, particularly in tackling piracy and maritime pollution.

However, reshaping the regional security architecture is another matter. Pitlo highlighted lingering hesitation over the idea of a collective security organization akin to an "Asian NATO" — a proposal Japan has promoted with some partners.

Instead, ASEAN states are more open to broader "minilateral" arrangements that go beyond security to include technology and investment, he said.

'Ugly reminders'

Roknifard said the "scars" of World War II have "certainly not healed" in the region, with "ugly reminders" surfacing at times. She pointed to online backlash in Malaysia following reports that Takaichi visited the Japanese Cemetery in Kuala Lumpur during an ASEAN Summit trip in October.

Anna Rosario Malindog-Uy, vice-president of the Asian Century Philippines Strategic Studies Institute in Manila, said Japan's military role in Southeast Asia still carries a historical baggage, contributing to a "quiet unease" as its military presence grows.

ASEAN leaders need to hedge to reconcile Japan's expanding military role with lingering World War II memories, she said.

Such hedging allows engagement without full alignment with Japan, while preserving balance in ties with other major countries such as China, she added. "ASEAN does not erase history but manages it."

Japan took part in Balikatan last year as an observer. This year, it is joining as an active participant for the first time.

Malindog-Uy warned that Japan's participation may set a precedent for other external powers to seek similar roles in Southeast Asia.

Ukeru Magosaki, director of the East Asian Community Institute in Tokyo and a former senior Foreign Ministry official, said Washington regards Beijing as a primary strategic threat and is advancing a framework linking Japan, the Philippines and China's Taiwan in a coordinated counterbalance, reflecting a high degree of policy coherence.

However, such measures are unlikely to fundamentally alter the regional balance of power, he said.

Hou Junjie in Tokyo contributed to this story.

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