BOSTON (AP) — A Massachusetts Air National Guard member who pleaded guilty to leaking highly classified military documents about the war in Ukraine is expected to be sentenced in federal court on Tuesday.

Prosecutors have argued that Jack Teixeira should be sentenced to 17 years in prison, saying he “perpetrated one of the most significant and consequential violations of the Espionage Act in American history.”

“As both a member of the United States Armed Forces and a clearance holder, the defendant took an oath to defend the United States and to protect its secrets — secrets that are vital to U.S. national security and the physical safety of Americans serving overseas,” prosecutors wrote. “Teixeira violated his oath, almost every day, for over a year.”

Teixeira’s attorneys will argue that U.S. District Judge Indira Talwani should sentence him to 11 years in prison. In their sentencing memorandum, they acknowledged that their client “made a terrible decision which he repeated over 14 months.”

“It’s a crime that deserves serious consequences,” the attorneys wrote. “Jack has thoroughly accepted responsibility for the wrongfulness of his actions and stands ready to accept whatever punishment must now be imposed.”

Teixeira, of North Dighton, Massachusetts, pleaded guilty in March to six counts of the willful retention and transmission of national defense information under the Espionage Act. That came nearly a year after he was arrested in the most consequential national security leak in years.

The 22-year-old admitted that he illegally collected some of the nation’s most sensitive secrets and shared them with other users on the social media platform Discord.

When Teixeira pleaded guilty, prosecutors said they would seek a prison term at the high end of the sentencing range. But the defense wrote that the 11 years is a “serious and adequate to account for deterrence considerations and would be essentially equal to half the life that Jack has lived thus far.”

His attorneys described Teixeira as an autistic, isolated individual who spent most of his time online, especially with his Discord community. They said his actions, though criminal, were never meant to “harm the United States.” He also had no prior criminal record.

“Instead, his intent was to educate his friends about world events to make certain they were not misled by misinformation,” the attorneys wrote. “To Jack, the Ukraine war was his generation’s World War II or Iraq, and he needed someone to share the experience with.”

Prosecutors, though, countered that Teixeira does not suffer from an intellectual disability that prevents him from knowing right from wrong. They argued that Teixeira’s post-arrest diagnosis as having “mild, high-functioning” autism “is of questionable relevance in these proceedings.”

The security breach raised alarm over America’s ability to protect its most closely guarded secrets and forced the Biden administration to scramble to try to contain the diplomatic and military fallout. The leaks embarrassed the Pentagon, which tightened controls to safeguard classified information and disciplined members found to have intentionally failed to take required action about Teixeira’s suspicious behavior.

Teixeira, who was part of the 102nd Intelligence Wing at Otis Air National Guard Base in Massachusetts, worked as a cyber transport systems specialist, which is essentially an information technology specialist responsible for military communications networks. He remains in the Air National Guard in an unpaid status, an Air Force official said.

Authorities said he first typed out classified documents he accessed and then began sharing photographs of files that bore SECRET and TOP SECRET markings. Prosecutors also said he tried to cover his tracks before his arrest, and authorities found a smashed tablet, laptop and an Xbox gaming console in a dumpster at his house.

The leak exposed to the world unvarnished secret assessments of Russia’s war in Ukraine, including information about troop movements in Ukraine, and the provision of supplies and equipment to Ukrainian troops. Teixeira also admitted posting information about a U.S. adversary’s plans to harm U.S. forces serving overseas.