A former member of the Massachusetts Air National Guard will spend 15 years in prison after he was sentenced Tuesday in federal court for illegally transmitting classified information in a case that illustrated the ease at which some of the nation’s most sensitive national secrets can spread online.

Jack Douglas Teixeira, 23, pleaded guilty in March 2024 to six counts of “willful retention and transmission of national defense information.” His defense team asked for an 11-year prison sentence while federal prosecutors in Boston pushed for him to spend 16 years behind bars.

Teixeira, wearing an orange prison jumpsuit, showed no visible reaction as U.S. District Judge Indira Talwani handed down the stiff prison sentence.

“I wanted to say I’m sorry for all the harm that I brought and caused,” Teixeira said. “I understand all the responsibility and consequences fall upon my shoulders alone and accept whatever that will bring.”

Teixeira enlisted in the Air National Guard in September 2019 as an information technology specialist and was assigned to the Otis Air National Guard base in Cape Cod. Despite his relatively low rank, he held a top-secret security clearance because of his job. Around January 2022, federal prosecutors said he began transferring classified information onto the Discord social media platform, a site popular with online gamers.

“Jack Teixeira made the choice day after day, week after week, for a year to share the nation’s secrets that were entrusted to him,” said Joshua Levy, the acting U.S. Attorney for the District of Massachusetts. “This significant sentence sends a powerful message to every individual who holds a top-secret clearance: Anyone who willfully threatens our national security by illegally disseminating classified information will face very serious repercussions.”

Prosecutors said Teixeira was assigned to the 102nd Intelligence Wing and used a secure workstation at the base to conduct hundreds of searches for classified documents containing national defense information unrelated to his duties as an information technology specialist. He was apparently motivated by a desire to impress his online correspondents with his access to classified material.

Teixeira was accused of obtaining and transmitting information about the ongoing conflict between Russia and Ukraine, including troop movements on a particular date based on sensitive U.S. intelligence that was gathered through classified sources and methods, officials said.

“Jack Teixeira caused enduring damage to our relationship with our allies and to our ability to gather information by revealing intelligence-gathering methods,” Mr. Levy said. “We won’t know the full extent of Jack Teixeira’s damage for several years.”

Teixeira’s former superiors at the base warned him on at least two occasions to stop conducting “deep dives” into classified intelligence information that had no relation to his job. In addition to passing along sensitive information he had copied while at work, Teixeira posted images of military documents on Discord that bore classification markings such as “Secret” and “Top Secret,” officials said.

Jodi Cohen, the head of Boston’s FBI office, called Teixeira “one of the most prolific leakers of classified information in American history.”

“His actions compromised military plans, sources, and methods and allowed our most significant adversaries access to some of our most closely-guarded intelligence. He knew that what he was doing was wrong – and was admonished for it – but he continued to do it anyway,” Special Agent Cohen said. “He told the FBI that he did this to boost his ego and impress his anonymous friends and to ‘set the record straight about Russia’s invasion of Ukraine.’”

Teixeira tried to obstruct the FBI investigation by destroying evidence and tampering with witnesses after he learned that investigators were closing in on him.

“This was not a victimless crime. The damage it caused will continue to impact our national security for decades,” Special Agent Cohen said.