Daniel Ellsberg: The 90-year-old whistleblower tempting prosecution

A tedious but consequential task kept Daniel Ellsberg busy for weeks from the end of 1969.

One by one, he photocopied thousands of top-secret documents that he hoped would end a long and costly conflict.

Known as the Pentagon Papers, the documents were part of a classified study that showed the extent of American involvement in the Vietnam War.

Mr Ellsberg famously leaked the study to newspapers in 1971 before facing espionage charges that were ultimately dismissed.

While the Pentagon Papers left a lasting legacy, they weren't the only documents Mr Ellsberg got his hands on.

At the same time, Mr Ellsberg copied another classified study that showed how seriously American military chiefs took the threat of nuclear war during the Taiwan crisis of 1958.