According to a Washington Post article published on Monday, Chinese military hackers began accessing classified defense networks in Japan in 2020. They gained information about the U.S. allies military capabilities and plans.

Former senior U.S. government officials said that the National Security Agency (NSA) discovered the hacking in the fall 2020. They described the invasion as persistent and deep, with hackers – cyberspies of the People’s Liberation Army – gaining access to military plans, capabilities, and assessments.

Upon hearing of the hack, the heads of NSA went to Tokyo to inform Japan’s Defense Minister. The minister then asked them to tell the Japanese Prime Minister themselves.

The hacks started under the Trump administration but continued into the Biden Administration as well. In 2021, officials discovered new information that revealed the continuing breach of Japan’s defence systems and the lack of progress made in stopping the leaks.

The Post reported that the U.S. and Japan agreed to hire a Japanese commercial company to assess vulnerabilities. The U.S. NSA/Cyber Command Team would then review the findings of the Japanese firm and make recommendations for how to close any gaps.

Forbes’ comment request to the State Department was not immediately responded to.