A federal judge sentenced a Massachusetts Air National Guardsman on Tuesday to 15 years in prison for posting secret intelligence reports online.

In court documents, the government has described the airman, Jack Teixeira, as among the most “prolific leakers” of classified information about national defense secrets in the country’s history.

“You are young and you have a future ahead of you, but it is such a serious crime,” the judge, Indira Talwani of Federal District Court in Massachusetts, told Airman Teixeira, 22, on Tuesday.

The government recommended a sentence of just under 17 years in prison. Airman Teixeira’s lawyer on Tuesday argued that his sentence should instead be 11 years.

The sentencing brings to an end a case that raised questions over how easily a relatively low-level member of the guard had obtained a top-secret clearance that gave him access to some of the country’s most sensitive secrets.

“I’m sorry for all the harm that I’ve wrought and that I’ve caused,” Airman Teixeira said. “I understand all the responsibility and consequences falls on my shoulders alone. And I accept whatever that may bring.”

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