A former Army Green Beret was sentenced Friday to more than 15 years in prison on espionage charges after he admitted to divulging military secrets to Russia for a 15-year period, authorities said. 

Peter Dzibinski Debbins, 46, of Gainesville, Va., conspired with Russian intelligence agents from December 1996 through January 2011, federal prosecutors said.

He pleaded guilty in November to violating the federal Espionage Act. Prosecutors sought a 17-year prison term. Debbins allegedly provided details on Special Forces activities overseas and the name of his fellow Special Forces members. 

"Debbins flagrantly and repeatedly sold out his country, including while he served as a Captain in the U.S. Army Special Forces," said Acting U.S. Attorney Raj Parekh for the Eastern District of Virginia. "The defendant’s brazen disclosures to Russian intelligence agents jeopardized U.S. national security and threatened the safety of his fellow servicemembers."

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This file booking photo provided by the Alexandria, Va, Sheriff's Office, shows Peter Debbins. Debbins, a former Army Green Beret who admitted divulging military secrets to Russia over a 15-year period was sentenced to more than 15 years in prison Friday on espionage charges.  (Alexandria Sheriff's Office via AP)

At his Friday hearing in Alexandria, Debbins said he was the victim of Russia's intelligence service, the GRU, and has put his life in danger for admitting he worked for them. 

"I have suffered in lonely silence for 25 years," he said. As for the danger he faces from the GRU, he said, "The GRU does not make threats; they keep promises."

Prosecutors said Debbins never mentioned being blackmailed during hours of interviews with the FBI. They said a more likely explanation is that he was disgruntled over his time in the Army and that he considered himself a "loyal son of Russia."

"The world has now observed that Russia successfully placed an espionage recruit within the elite U.S. Army Special Forces, a propaganda victory for Russia at the expense of the reputation of the Special Forces," prosecutors Thomas Traxler and James Trump wrote in their sentencing brief.

Debbins' relationship with Russian intelligence began when he was an ROTC student at the University of Minnesota. During a visit to Russia, he gave a handler the names of four Catholic nuns he had visited after a Russian intelligence agent told him the nuns were involved in cult activity.

He had already committed to serving Russia in writing when he entered the Army in 1998. He was assigned the code name "Ikar Lesnikov."

"I had a messianic vision for myself in Russia, that I was going to free them from their oppressive government, so I was flattered when they reached out to me," Debbins wrote in a handwritten confession.

Debbins was dishonorably discharged in 2004 when he was a captain assigned to Azerbaijan. His discharge stemmed from a security violation in which he relocated his wife to the country and provided her with a U.S. government cell phone.

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In 2008, he traveled to Russia and gave intelligence agents information about old Special Forces unit's activities in Georgia and Azerbaijan. A damage assessment of what Debbins disclosed was filed under seal — Debbins said in sentencing papers that he thought he only gave the Russians information they already knew.

Debbins received nominal payments for his information, even though he initially refused an offer of a $1,000 cash payment. In one meeting with Russian intelligence, he accepted a bottle of Cognac and a Russian military uniform as payment, according to the indictment.

The Associated Press contributed to this report.