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 on Thursday, the Pentagon spokesman 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 office also developed inventive ways of fighting adversaries. Jim Baker, a retired Air Force colonel, succeeded Mr. Marshall in 2015.
The office’s influence often depended on the defense secretary’s priorities and personal relationship with its director. In the early 2000s, Defense Secretary Donald Rumsfeld relied heavily on Mr. Marshall to develop ways of fighting that relied on speed, precision munitions and rapidly improving surveillance capabilities to quickly defeat adversaries.
More recently, the office focused on developing concepts for a possible war with China. It championed a concept called Air-Sea Battle, which envisioned an initial “blinding campaign” by stealthy U.S. bombers and submarines that would knock out China’s long-range surveillance radar followed by a larger naval assault.
Thomas G. Mahnken, a former top Pentagon strategist, questioned the decision to dismantle an office focused on preparing the U.S. military for long-term competition with major powers at a time when China seems to be growing stronger and more aggressive.
“We’re in a period that looks a lot like the Cold War, and we’re doing away with an office that for decades helped senior leaders navigate that conflict,” said Mr. Mahnken, who leads the Center for Strategic and Budgetary Assessments, a defense think tank based in Washington.
Senator Jack Reed, Democrat of Rhode Island, similarly called the office’s closing “shortsighted,” adding that it would “undermine our ability to prepare for future conflicts.”
The office’s critics, such as Senator Charles E. Grassley, Republican of Iowa, have charged that it has not received enough scrutiny in recent years. In a statement released on Thursday, Mr. Grassley blasted the internal Pentagon think tank as “wasteful and ineffective.”
Other critics have said that it has too often ignored the wars the Pentagon was actually fighting in Iraq and Afghanistan in favor of future and potentially distant threats.
The office’s core mission is to compare or assess opposing sides in a potential conflict, typically the U.S. military and its most capable or advanced adversary. Over the decades, the Office of Net Assessment conducted thousands of war games, often in partnership with the military services or think tanks. And it produced countless studies.
“Many of the products were highly classified,” Eliot A. Cohen, a former State Department official and political scientist, wrote in The Atlantic in 2019. “Some were well known (such as his iconic assessment of the standoff in Central Europe during the Cold War) and some went to only one or two consumers.”
The Office of Net Assessment often focused on high-risk research that others in the Pentagon were unlikely to undertake. As a result, its work sometimes did not produce tangible or immediate results for the military.
The Pentagon statement said that all of the office’s personnel would be assigned to “mission-critical roles” in the Defense Department but did not specify what those positions might be.