Jack Smith, the special counsel who brought two failed federal prosecutions against President-elect Donald J. Trump, resigned this week, according to a footnote buried in court papers — a remarkably muted conclusion to a fight that reshaped the nation’s legal and political landscape.

Mr. Smith, a former war crimes prosecutor who fought a bitter and protracted battle on two fronts with the Trump legal team but lost in both a district court and in the Supreme Court shaped by Mr. Trump, left his offices in Washington on Friday, according to a senior law enforcement official.

His departure was expected. Mr. Smith had signaled his intention to leave before Mr. Trump, who had threatened to fire and punish him, took office on Jan. 20.

In the end, Mr. Smith made no formal announcement. His spokesman had no comment.

The special counsel departed after his efforts in the courtroom were essentially rendered moot by Mr. Trump’s political victory in November. Under a Justice Department policy prohibiting the pursuit of prosecutions against a sitting president, Mr. Smith was compelled to drop both of the cases he had filed against Mr. Trump in 2023 — one in Florida, accusing him of mishandling a trove of classified documents, and the other in Washington, on charges of plotting to overturn the 2020 election.

Mr. Smith’s final week was marked by one more legal setback at the hands of Judge Aileen M. Cannon, the Trump-appointed jurist presiding over the Florida documents case: She temporarily blocked public release of his final report until at least Monday.

The monumental legal saga, which embittered Mr. Trump and steeled him for his remarkable return to power, ended with a single line at the bottom of the last page of a brief sent to Judge Cannon on Saturday: “The special counsel completed his work and submitted his final confidential report on Jan. 7, 2025, and separated from the department on Jan. 10.”