“Joshua Schulte betrayed his country by committing some of the most brazen, heinous crimes of espionage in American history,” said US Attorney Damian Williams.

According to evidence shared at the trial, Schulte was employed as a software developer in the Center for Cyber Intelligence, which conducts cyber espionage against terrorist organisations and foreign governments.

Prosecutors said that in 2016 that he transmitted the stolen information to Wikileaks and then lied to FBI agents about his role in the leak.

They said that he was seemingly motivated by anger over a workplace dispute.

Schulte had been struggling to meet deadlines and Assistant US Attorney Michael Lockard said one of his projects was so far behind schedule that he had earned the nickname “Drifting Deadline”.

The prosecutors said he wanted to punish those he perceived to have wronged him and said in “carrying out that revenge, he caused enormous damage to this country’s national security”.

Wikileaks began publishing classified data from the files in 2017.