Defense Strategy in Focus as China Escalates in East and South China Seas

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On May 31, the defense ministers of Japan, the United States, Australia, and the Philippines met in Singapore. In a joint statement, they expressed "continued serious concern about China’s destabilizing actions in the East China Sea (ECS) and the South China Sea (SCS) and any unilateral attempts to change the status quo by force or coercion."

The four nations also "committed to continue working together and with other like-minded partners to support peace, stability, and prosperity in the Indo-Pacific."

Participants included Japan's Defense Minister Gen Nakatani, US Secretary of Defense Pete Hegseth, Australian Defense Minister Richard Marles, and Philippine Defense Secretary Gilbert Teodoro. 

During the meeting, Nakatani noted China has become more active than ever in the East and South China Seas. 

This was the third meeting of the four defense ministers since May 2024. In the joint statement, they also agreed to develop their partnership in the four key areas of defense investments, information-sharing, cybersecurity and resilience, operational coordination and interoperability.

Separately, Japan, the US, and Australia held a trilateral defense meeting. During the talks, the three nations agreed to conduct live-fire exercises and deepen cooperation related to Tomahawk cruise missiles, which Japan and Australia are procuring from the United States.

Cybersecurity, Strategy, and Regional Vision

In the bilateral Japan-US defense talks, the two sides agreed to strengthen cybersecurity cooperation. This move follows the passage of legislation in Japan enabling proactive cyber defense. They also confirmed plans to coordinate closely on the newly formulated American National Defense Strategy (NDS). 

When asked by reporters whether the US had requested Japan increase its defense spending, Nakatani declined to comment.

That same day, Nakatani followed up these meetings with a speech at the Shangri-La Dialogue, an Asia security summit. "We will work to restore a rules-based international order in the Indo-Pacific," he promised. He also stressed that through cooperation on defense equipment and other measures, "Japan will remain ASEAN's and the region's best partner."

Engaging Trump's Attention

The four-nation Japan-US-Australia-Philippines defense ministers' meeting additionally signaled the desire to continue multilateral cooperation. With China's defense budget now more than four times Japan's, maintaining deterrence will require more than just the US-Japan alliance. Stronger ties with Australia and the Philippines, which face similar threats, are also essential.

In February 2025, the four countries conducted cooperative maritime exercises in the South China Sea. China continues to face off with the Philippines by building artificial islands and expanding CCP military bases in waters under Manila's administrative jurisdiction. Meanwhile, in the seas off Australia, the Chinese navy has conducted live-fire drills. 

Both Australia and the Philippines face territorial intrusions, as Japan does around the Senkaku Islands in Okinawa Prefecture. All three are contending with increasing Chinese military pressure.

The framework of Japan-US-Australia-Philippines cooperation was launched under the previous Joe Biden administration. President Donald Trump has shown reluctance toward multilateral frameworks that limit US autonomy. Nevertheless, Japan, Australia, and the Philippines now appear to be aligning closely in hopes of drawing Trump's attention and securing continued US engagement.

Japan is also advancing bilateral defense cooperation with both Australia and the Philippines. It has designated Australia as a "quasi-ally," second only to the US, and has plans to collaborate in developing counterstrike capabilities. Through direct assistance, Japan has provided the Philippines with air defense radar systems. Should the radar data eventually be shared with Japan's Self-Defense Forces, "movements of the Chinese military would be fully visible," according to a former defense minister.

South Korea, Absent but Essential

Notably absent from the latest talks was South Korea. In the event of a Taiwan contingency, Seoul's cooperation would be critical to deter provocations or escalation from North Korea. However, with South Korea in a transition period ahead of its presidential election, no minister-level official was dispatched to the security summit. 

All five countries ー Japan, the US, Australia, the Philippines, and South Korea ー met for the first time in November 2024. A senior official at Japan's Ministry of Defense admitted, "We had hoped for all five nations to gather again."

Defense cooperation between Japan and South Korea has effectively stalled since former President Yoon Suk-yeol declared a martial law emergency in December 2024. Nakatani is exploring an early visit to South Korea following the June 3 presidential election with a view to restarting engagement.

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Author: Shusuke Takenouchi, The Sankei Shimbun

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