BERLIN

A former German military officer admitted on Monday that he had offered himself as a spy to Russia, telling a court that he had done so out of fear of a nuclear escalation in the Ukraine war.

On the first day of his trial, Thomas H. told judges at the higher regional court in Dusseldorf that last year he had psychological problems, feared a nuclear escalation, and wanted to ensure the safety of his family.

The 54-year-old admitted that he had contacted Russian diplomatic representations in Germany, acknowledged that he shared some documents, but claimed that they did not include any serious information.

He also admitted that he applied to become a member of the far-right Alternative for Germany (AfD) and joined the party last year.

The former military officer was arrested last year in the western city of Koblenz. He was an employee at the Federal Office of Bundeswehr Equipment, Information Technology and In-Service Support.