Colonel Spath and prosecutors have portrayed the mass resignation by the defense lawyers as essentially a stunt strategically timed to delay or derail the case, suggesting there was no basis for their concerns. Because the basic details were classified until recently, the defense lawyers have been limited in what they could say to rebut those accusations.

But the claim that the government had never previously put forward the explanation for the microphone sheds new light on the intensity of the recent sparring. Lt. Alaric Piette of the Navy, the only remaining lawyer representing Mr. Nashiri, also said the newly declassified statement was the first time the government said that the microphone was a legacy device and that a wire leading from it into the wall was not hooked up to anything.

“If you look at the microphone, there is no indication it is unhooked. If it is legacy, you can’t tell,” he said, adding, “We had not heard anything of this before.”

The declassified statement and the interviews with the two defense lawyers also filled in other details about the highly disruptive incident in one of the most important war-crimes cases arising from the conflict with Al Qaeda.

For example, Mr. Kammen said Mr. Nashiri’s defense team had already grown suspicious that its conversations with its client might be subject to surreptitious monitoring because of an earlier incident, although he said he could not describe it because its details might be classified.

“There was at least one episode, I’m comfortable saying, that absolutely caused us to believe that there was ongoing eavesdropping,” he said.

In April 2017, the statement said, it came to light that confidential conversations involving other detainees and their lawyers elsewhere in the prison complex had been “unintentionally overheard.” As a result, Brig. Gen. John Baker, who oversees military commissions defense lawyers, sent an email in June warning all defense lawyers of confidentiality problems.