The Government Accountability Office says a Pentagon hiring freeze and a wave of voluntary staff departures have left many of the U.S. military's most expensive weapons programs short-staffed, threatening delays and eroding civilian expertise built up over years.

In an annual review of 48 of the costliest and most complex U.S. weapons programs published Thursday, the watchdog found the Defense Department has been unable to backfill acquisition jobs vacated under a Deferred Resignation Program launched last year by President Donald Trump's administration.

More than 48,000 Defense Department employees, over 6% of the civilian workforce, were approved to leave under the program as of June 2025, the report found.

GAO said exits tied to 37 of the department's key procurement programs have drained institutional knowledge and threatened work on critical vehicles and munitions, and a hiring freeze ordered last year has made it harder for more than half of the 48 program offices GAO reviewed to bring on replacements.

One office lost nearly 40% of its core staff in 2025 and managed to backfill only a third of the vacancies, according to the report.

Another lost 31 employees to the resignation program, almost 6% of its workforce.

"One program lost seven civilian positions due to the DRP, and it has not been able to backfill due to the ongoing hiring freeze," GAO wrote, adding that the remaining staff has absorbed the same workload, including working weekends, to avoid delays.

Filling acquisition jobs is difficult in the best of circumstances, GAO noted, citing a shallow pool of specialized candidates, higher private-sector pay, and a federal hiring process that can take several months to complete.

One program had to advertise a position multiple times before finding a qualified applicant, and another said it can take a new hire roughly a year to become fully productive.

DoD pledged last year to cut up to 8% of its nonuniformed workforce to align staffing with national security priorities.

"We are confident that we can absorb [DRP] removals without detriment to our ability to continue the mission," a senior defense official said in March 2025.

Eight months later, Defense Secretary Pete Hegseth announced a broader Acquisition Transformation Strategy aimed at rebuilding recruitment and retention of skilled acquisition staff over time, Federal News Network reported.

GAO said the department has not yet fully determined the effects of the workforce changes and will continue monitoring them.

The agency has flagged similar acquisition-workforce problems for years; the department has concurred with its recommendations but has made little progress in implementing them, and military acquisition remains on GAO's high-risk list of programs most vulnerable to waste, fraud, and abuse.