With the Iraq war over and troops in Afghanistan on their way home, the U.S. military is getting down to brass tacks: culling generals and admirals from its top-heavy ranks.

Pentagon officials said they have eliminated 27 jobs for generals and admirals since March, the first time the Defense Department has imposed such a reduction since the aftermath of the Cold War, when the collapse of the Soviet Union prompted the military to downsize.

The cuts are part of a broader plan to shrink the upper ranks by 10 percent over five years, restoring them to the their size when the country was last at peace, before the attacks of Sept. 11, 2001.

The changes are projected to save only a modest amount of money, but defense officials said they are symbolically important as the Pentagon adjusts to an era of austerity. The Obama administration proposes to squeeze $450 billion from defense budgets over a decade. An additional $500 billion in cuts will be triggered if Congress cannot agree on a deficit-reduction plan in the next year.

Thinning the ranks of generals and admirals is also necessary to make the military more nimble, said Vice Adm. William E. Gortney, director of the Joint Staff at the Pentagon.

“If 10 years of combat have taught us anything, it’s that flat is faster,” said Gortney, who was appointed last year by then-Defense Secretary Robert M. Gates to review the number of top officers.

In March, Gates approved a plan to reduce the number of authorized billets reserved for generals and admirals from 952 to 850, giving the armed services five years to implement the changes.

In addition, 23 billets will be downgraded in rank; a job previously reserved for a three-star general, for example, will now go to a two-star.

Gortney said the military has eliminated 27 command slots since then — many of them key positions from the war in Iraq — leaving the Pentagon more than a quarter of the way to its goal of cutting 102 jobs.

Other command jobs are falling by the wayside as part of reorganizations that are eliminating the Army’s Accession Command, based at Fort Knox, Ky., and the Navy’s Second Fleet, based in Norfolk.

‘Brass creep’

In ordering the cuts, Gates said the military had succumbed over the years to “brass creep,” by adding a disproportionate number of jobs at the top. The number of four-star generals and admirals today, for instance, is roughly the same as in 1971, during the Vietnam War, even though the number of active-duty troops has shrunk by half.

The Army, Air Force, Navy and Marine Corps are all expected to continue shrinking because of budget cuts, the end of the war in Iraq and the Obama administration’s planned withdrawal from Afghanistan.

Leon E. Panetta, the current defense secretary, backs Gates’s plan, according to Pentagon press secretary George Little. “The Secretary supports this initiative, and he is pursuing it in a way that ensures that outstanding leadership remains an indelible hallmark of the U.S. military,” Little said in an e-mail.

Some lawmakers, after years of questioning growth at the top, have praised the Pentagon for committing to a smaller military leadership. “The fact of the matter that you are looking . . . to deal with star creep is a very good thing,” Sen. Lindsey O. Graham (R-S.C.) told Defense Department officials at an Armed Services subcommittee hearing in September.

Critics, however, have accused the Pentagon of dragging its feet. Benjamin Freeman, a national security analyst at the nonpartisan Project on Government Oversight, said the number of generals and admirals on active duty stood at 970 as of Sept. 30.That represented an increase of six active-duty positions from March, when Gates ordered the cuts. (The Pentagon released updated figures this week, showing 966 generals and admirals on active duty as of Oct. 31, the most recent data available.)

“They made a fairly convincing argument that they had the situation under control and that they were moving full speed ahead, so it’s been depressing to see,” Freeman said.

In an interview, Gortney said thefigures are misleading because they include several officers who have since retired or are in the process of taking other slots.

He said the armed services have up to two years to phase out a job targeted for elimination. “You need time to work this,” he added. “You can’t just give people their pink slips.”

Four categories

Gortney said the Pentagon review ordered each branch of the armed services to sort their generals and admirals into four categories: “must have,” “need to have,” “good to have” and “nice to have.”

At least 10 percent had to fall into the “nice to have” category, he said. In the end, many of those were axed. “We mandated that you had to put the low-hanging fruit in there,” Gortney said. “We made them defend every one of their positions.”

Of the 102 positions slated to be cut, nearly half — 47 — are commands from Iraq, Afghanistan or other overseas operations.

The vast majority — 90 slots — have been reserved for one- or two-star generals and admirals.

The only four-star jobs pegged for elimination are the commander of U.S. forces in Iraq, the commander of U.S. and NATO forces in Afghanistan, and the commander of the U.S. Army in Europe.

Military leaders said they are concerned that drastic cuts in the numbers of admirals and generals could make it more difficult to promote and retain promising officers. Those effects are already being acutely felt further down in the ranks.

In the Army, for example, only 36 percent of this year’s regular class of lieutenant colonels seeking promotion were accepted as colonels, the lowest percentage since 1987, according to Gen. Ray Odierno, the Army chief of staff.

In a Dec. 20 e-mail to officers, Odierno acknowledged that this year’s low promotion rate to colonel “generated significant interest and concern by leaders across the Army.”

Odierno said that the service had an excess of colonels and that this year’s class of promotion-eligible lieutenant colonels was unusually large. In contrast, he noted that five years earlier, at the height of the Iraq war, the same class won promotion from major to lieutenant colonel at a rate of 91 percent.

He said he expected officer promotion rates to return to levels that were common before 2001 — or sink even lower — as the Army prepares to shrink over the next decade.

“Some great officers will not be selected,” he wrote in his e-mail. “This is difficult for those that have served honorably and with distinction during very demanding times for our Army.”