WASHINGTON — The Trump administration has freed an American citizen whom the military imprisoned without trial for more than 13 months as a suspected Islamic State member, United States officials said on Monday. His release brings a close to a legal saga that raised novel issues about the scope of the government’s national security powers and individual rights.

The man, a dual American and Saudi citizen, was captured in September 2017 by a Kurdish militia in Syria. The Kurds turned him over to the American military, which held him as a wartime detainee at a base in Iraq while a court battle over his fate played out. The officials, who spoke on condition of anonymity, said he was released in Bahrain, where his wife and daughter are living.

The identity of the man at the center of the extraordinary case has been kept secret, so he has been called “John Doe” in court filings and public debates. But his real name is Abdulrahman Ahmad Alsheikh, The New York Times has learned, in part by obtaining an unredacted version of his Islamic State intake form and identifying public records about him.

His release means that a major question his detention raised about how the United States fights war — whether the government has authority to use wartime powers against the Islamic State without explicit congressional authorization — will evade a definitive court ruling, for now. Even so, his case established an important historical precedent: The American government locked up a citizen for more than a year without charging him with a crime.