Last year Japan lifted a decades-long ban on military exports, part of a loosening of restrictions on its military power that were put in place after its World War Two defeat. Now, as Japanese companies such as Mitsubishi, Kawasaki, and Hitachi market their military offerings, one area of geopolitical tension is serving as a particularly effective selling point: the South China Sea.

This weekend Japan’s foreign and defense ministers reiterated concerns about China’s strengthening position in the South China Sea as they pressed the case, according to Bloomberg, for their Australian counterparts to buy a new generation of submarines made by Japanese defense contractors.

Defense minister Gen Nakatani sought to cast the bid in the context of freedom of the seas. “Both of our nations are maritime nations and we have a key interest in freedom of navigation,” he said on Sunday (Nov. 22), according to Bloomberg.

And last week Japan broadly agreed to transfer defense equipment and technology to the Philippines, which has been the most vocal opponent of Beijing’s territorial claims in the South China Sea, even taking up a case with an international tribunal in the Netherlands.

Beijing claims nearly all of the sea as its own territory, citing a “nine-dash line” that China drew up at the end of World War Two. That claim is considered outrageous by various Asian nations that have conflicting claims, and by the US, which has long viewed the sea—a vital trade route—as international waters.

To bolster its claim, China has been busy building artificial islands in the Spratly archipelago, complete with a runway, helipad, and lighthouse.

To counter Beijing’s assertiveness, the US has been conducting “right of navigation” exercises in the South China Sea. Since late October it’s sent a warship and B52 bombers near China’s artificial islands.

Japan has not joined in such operations. “With regard to activity by the Self-Defense Forces in the South China Sea, I will consider it while focusing on what effect the situation has on Japan’s security,” Japanese prime minister told Shinzo Abe told US president Barack Obama last week, according to Bloomberg. Chief cabinet secretary Yoshihide Suga was quick to note Abe’s comments did not indicate an actual change in policy, and that Japan is not currently planning to take part in US operations.

But Indonesia, Taiwan, Vietnam, and the UK have all expressed interest in Japan’s military hardware, and there is already a deal pending with India.

Resentment over Japan’s aggression during World War Two still runs deep in China. As Zhu Chenghu, a professor of strategic studies at China’s National Defense University, told CNBC in June:

“The United States used to have military bases in Southeast Asia, like in the Philippines and even in Vietnam, and they have military cooperation with Singapore, so American military presence in the South China Sea is acceptable to China… As for the Japanese military presence, it is very difficult for the Chinese people and the Chinese government to accept it.”

Even if Japan doesn’t get involved in a direct military fashion in the South China Sea, it can still play a role in supplying the contestants.