The defendant, only partially named as Martin D., was put on trial in a German court in the western city of Koblenz, with proceedings held partly behind closed doors.

In 2024, prosecutors charged that Martin D. had "contacted Chinese government agencies several times and offered to pass on sensitive information from the US military to a Chinese intelligence service".

The man worked as a contractor for the US Defense Department between 2017 and 2023, including at a US military base in Germany since at least 2020, according to the indictment.

He was arrested by German police in Frankfurt in November 2024 and has been held in pretrial detention since.

The United States established dozens of bases in Germany after World War II, and still has more than 35,000 US troops stationed in the country.

The bases -- located mostly in the former US military occupation zone in western and southern Germany -- also employ approximately 11,000 civilians for services such as logistics, catering, healthcare and security.

Germany has seen an increase in suspected spying cases linked to Russia since the 2022 start of the full-scale invasion of Ukraine, with German authorities accusing Moscow of waging "hybrid warfare" -- something that Moscow denies.

But there have also been a number of espionage cases linked to China, with Berlin's ties to Beijing under growing pressure.

In the most high-profile recent case involving China, a former aide to German far-right politician Maximilian Krah was jailed for four years and nine months in September on spying charges.

A court in Dresden found Jian Guo guilty of acting as an agent for a Chinese intelligence service while working for Krah, a member of the anti-immigration Alternative for Germany (AfD) party.