Japan has signed its most consequential international defence agreement in decades, finalizing a A$10 billion ($6.5 billion) deal on Tuesday to supply Australia with state-of-the-art warships. The agreement, hailed as a milestone in Japan’s postwar military posture, reflects a significant shift toward proactive regional security cooperation.

Under the deal, Mitsubishi Heavy Industries (MHI) will build and deliver the first three upgraded Mogami-class multi-role frigates to the Royal Australian Navy starting in 2029. The highly advanced ships are capable of submarine detection, surface attacks, and air defense missions. Notably, the frigates are designed for efficiency, operating with crews of just 90—less than half the personnel required by current Australian naval vessels.

Australian Deputy Prime Minister and Defence Minister Richard Marles praised the agreement as a strategic investment in national defense. “These warships will significantly enhance our navy’s ability to project power and protect our vital interests across the Indo-Pacific,” Marles said.

The new vessels are expected to strengthen Australia’s maritime defenses amid growing tensions in the region, particularly due to increased Chinese naval activity. They will also help secure crucial sea lanes and reinforce Australia’s northern maritime approaches.

For Japan, the deal represents a breakthrough in its efforts to expand defense partnerships beyond the U.S.-Japan alliance. Japanese Defence Minister Gen Nakatani called the agreement “a major step forward” in building deeper military interoperability with Australia and the United States.

The deal also marks a comeback for Japan after its submarine bid was rejected by Australia in 2016 in favor of a now-canceled French project. That decision was overturned in 2023 when Australia committed to acquiring nuclear-powered submarines under the AUKUS pact with the U.S. and U.K.

Of the eleven planned frigates, MHI will construct the first three in Japan, while Australian shipbuilder Austal is expected to produce the remaining eight in Western Australia. The collaboration is set to deepen industrial and technological cooperation between the two nations.

MHI noted in a statement that the deal “will enhance the scientific and technical workforce and bolster the defense industrial base in both countries,” marking a significant step forward in Japan’s global defense role.