The deal ends a period of confinement that lasted about a dozen years, first in the self-exile of the Ecuadorean embassy in London, then in prison.
Julian Assange spent his youth in Australia during the 1980s in a state of chaotic, perpetual motion. He moved more than two dozen times, bounced from school to school and was thrust, for a time, into what he called a New Age cult, before settling in Melbourne.
It was there, at age 16, that he adopted a calling: hacking. It would eventually place him on the edge of global disruption in an era of backlash against the national security and political establishments.
Mr. Assange, the 52-year-old founder of WikiLeaks, boarded a private jet this week from London for the long flight to a U.S. courtroom in Saipan, where he pleaded guilty on Wednesday to a single count of illegally obtaining and disseminating national security information.
A brief proceeding in a remote outpost capped a long legal saga.
For a case that attracted a spotlight for more than a decade, its final throes played out quickly and in relative obscurity.
Mr. Assange, wearing a black suit, offered his plea in a federal court in Saipan, the capital of the U.S. commonwealth of the Northern Mariana Islands in the Western Pacific. He had refused to appear in court on the U.S. mainland and asked that the hearing be at the remote judicial outpost, which is near his native Australia.
He responded carefully to questions from U.S. District Judge Ramona Manglona and defended his actions, describing himself as a journalist seeking information from sources, a task he said he saw as constitutionally protected.