WASHINGTON — Defense Secretary Pete Hegseth ordered the shuttering of the Office of Net Assessment, a small, often secretive and sometimes opaque office that for more than 50 years has helped the Pentagon’s most senior leaders think about the future of war.

The office costs about $10 million to $20 million a year — a fraction of the Pentagon’s $850 billion annual budget — but its work and staff of about a dozen civilians and military officers has often had an outsize impact on how the Pentagon prepares for possible conflicts.

In a short note posted Thursday, Pentagon spokesperson Sean Parnell suggested that the office would be restructured and then reopened with a new focus on the country’s most “pressing national security challenges.” He did not explain how the office’s new mission would differ from its previous approach.

For most of its history, the Office of Net Assessment was run by Andy Marshall, its founder, who pioneered an innovative and somewhat mysterious approach to comparing the strength of U.S. forces with that of its potential enemies. — The New York Times