MIAMI — President Trump improperly shared a Pentagon “plan of attack” and a classified map related to a military operation, according to a sweeping 37-count felony indictment related to the mishandling of classified documents that was unsealed Friday and that could instantly reshape the 2024 presidential race.

The indictment paints an unmistakably damning portrait of Mr. Trump’s treatment of sensitive information, accusing him of willfully defying Justice Department demands to return documents he had taken to Mar-a-Lago from the White House, enlisting aides in his efforts to hide the records and even telling his lawyers that he wanted to defy a subpoena for the materials stored in his estate.

“I don’t want anybody looking through my boxes,” one of Mr. Trump’s lawyers described the former president saying, according to the indictment. He also asked if it would be better “if we just told them we don’t have anything here,” the indictment says.

Making his first public statements, the Justice Department special counsel who filed the case, Jack Smith, said: “Our laws that protect national defense information are critical to the safety and security of the United States and they must be enforced. Violations of those laws put our country at risk.”

He added, “We have one set of laws in this country and they apply to everyone.”

The indictment arrives at a time when Mr. Trump is continuing to dominate the Republican presidential primary and one day before a scheduled campaign trip to North Carolina. Though other candidates have largely attacked the Justice Department, rather than Mr. Trump, for the investigation, the indictment’s breadth of allegations and startling scope could make it harder for Republicans to rail against than an earlier New York criminal case that many legal analysts had derided as weak.

The 49-page charging document, alleging that Mr. Trump not only intentionally possessed classified documents but also cavalierly and boastfully showed them off to visitors, is startling in scope and in the breadth of allegations. The indictment is built on Mr. Trump’s own words and actions as recounted to prosecutors by lawyers, close aides and other witnesses, with prosecutors even using against Mr. Trump his own words as a candidate and president professing to respect and know procedures related to the handling of classified information.

The indictment includes 37 counts — 31 of which pertain to the willful retention of national defense information, with the balance relating to alleged conspiracy, obstruction and false statements —that taken together could result in a yearslong prison sentence.

Mr. Trump is due to make his first court appearance Tuesday in federal court at Miami. He was charged alongside Walt Nauta, an aide and close adviser to Mr. Trump who prosecutors say brought boxes from a storage room to Mr. Trump’s residence for him to review and later lied to investigators about the movement. A photograph included in the indictment shows several dozen file boxes stacked in a storage area.

Noting the “tens of thousands of members and guests” who visited the “active social club” of Mar-a-Lago between the end of Mr. Trump’s presidency in January 2021 through the August 2022 search, prosecutors argued that Mr. Trump had “nevertheless” stored the documents there, “including in a ballroom, a bathroom and shower, and office space, his bedroom, and a storage room.”

The case adds to deepening legal jeopardy for Mr. Trump, who has already been indicted at New York and faces additional investigations at Washington and Atlanta that also could lead to criminal charges. Yet among the various investigations he has faced, legal experts — as well as Mr. Trump’s own aides — had long seen the Mar-a-Lago probe as the most perilous threat and the one most ripe for prosecution. 

Enumerating the defense and foreign intelligence-related information included in the documents, prosecutors wrote that their “unauthorized disclosure … 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 collection methods.”