A US court on Monday sentenced a Chinese engineer to more than five years in prison following his conviction for illegally exporting military trade secrets to China.

Liu Sixing, a former defence engineer at US company L-3 Communications’ space and navigation unit, was convicted in 2012 of exporting military information, possessing stolen trade secrets and lying to authorities, BBC reports.

Liu, also known as Steve Liu, stole thousands of files in 2010, including information on the performance and design of guidance systems for missiles, rockets and unmanned drones.

He then gave presentations about the technology he was working on at Chinese universities and government-organized conferences without L-3’s permission, hoping it would help him gain future employment in China, reports Al Jazeera.

He was arrested in November 2010 after federal agents discovered the files on his computer when he returned to the US.

Liu said he did not break the law, or intend to pass secrets to China. James Tunick, the defendant’s lawyer, said that Liu had made “a terrible mistake” by having the files on his computer and taking them to China, but that “it didn’t rise to the level of a criminal act.”

Technical military data covered by US export regulations cannot be taken out of the country without a license, according to BBC.

“Instead of the accolades he sought from China, Sixing Liu today received the appropriate reward for his threat to our national security: 70 months in prison,” prosecutor Paul Fishman said.