Federal prosecutors unsealed indictments on Friday against former President Donald J. Trump and one of his personal aides, Waltine Nauta, revealing devastating new details about a more than yearlong investigation into Mr. Trump’s handling of classified material.

The 49-page indictment, containing 38 counts and seven separate charges, gave the clearest picture yet of the files that Mr. Trump took with him when he left the White House. It said he had illegally kept documents concerning “United States nuclear programs; potential vulnerabilities of the United States and its allies to military attack; and plans for possible retaliation in response to a foreign attack.”

“The unauthorized disclosure of these classified documents could put at risk the national security of the United States, foreign relations, the safety of the United States military, and human sources and the continued viability of sensitive intelligence collections methods,” the indictment said.

The indictment described Mr. Trump as willfully hanging onto documents that were called by some aides “his papers.” It detailed how Mr. Trump suggested to one of his lawyers that it was possible to tell prosecutors that “we don’t have anything here” after a grand jury subpoena had been issued for all remaining classified material in his possession.

“I don’t want anybody looking through my boxes, I really don’t,” Mr. Trump also told the lawyer during that meeting, according to the indictment.

In many ways, much of the story told in the indictment has been publicly known for months amid extensive news media reporting on the investigation. And yet for all that information, the public had only a keyhole view into the volume of evidence the government had amassed.

There were fresh details like a sensitive “Five Eyes” intelligence record spilling out of a box onto the floor of storage room at Mar-a-Lago, Mr. Trump’s club and residence in Florida.

And there was shock value to the fact that Mr. Trump, who has spent years avoiding having people close to him take notes of his conversations, being charged in part based on notes from one of his lawyers and an audiotape of a meeting that he was aware was being recorded.

According to his lawyers’ notes, Mr. Trump made a “plucking motion” that he believed implied, “why don’t you take them with you to your hotel room and if there’s anything really bad in there, like, you know, pluck it out.”

The indictment laid out a conspiracy between Mr. Trump and Mr. Nauta who is said to have moved roughly 64 boxes from a storage room at Mar-a-Lago to Mr. Trump’s residence at the compound. The indictment said that Mr. Nauta returned only about 30 boxes to the storage room, apparently leaving the rest unaccounted for.

On top of all that, prosecutors presented evidence that Mr. Trump had shared a highly sensitive “plan of attack” against Iran to visitors at his golf club in Bedminster, N.J. in July 2021 — and was recorded on tape describing the material as “highly confidential” and “secret,” while it admitting it had not been declassified. In another incident in September 2021, he shared a top secret military map with a staff member at his political action committee who did not have a security clearance.

It is unusual for prosecutors to unseal an indictment before a defendant shows up in court for an initial appearance. But the decision to release the document in this case came as Mr. Trump and his allies had been aggressively attacking the investigation and, in the view of federal law enforcement officials, distorting elements of the case.

The move was in keeping with the Justice Department’s practice, under Attorney General Merrick B. Garland, of releasing information to the public through their filings in court — a tactic the department deployed to release the detailed affidavit used to justify the search of Mr. Trump’s residence in Florida last August.