The Pentagon's plan to shrink the size of the Army and Marine Corps for the first time in two decades is unlikely to stave off pressure to impose deeper cuts as U.S. troops pull out of Iraq and Afghanistan, according to defense officials and analysts.
"This is the opening salvo," said David W. Barno, a retired Army lieutenant general and former commander of U.S. forces in Afghanistan.
In a bid to save money, Defense Secretary Robert M. Gates announced Thursday that the Marine Corps would shed between 15,000 and 20,000 members and the Army 27,000 soldiers starting in 2015, the first time either service has faced reductions in troop strength since the mid-1990s.
The cuts are timed to coincide with what is expected to be a large-scale withdrawal of U.S. forces from Afghanistan, where the Kabul government has pledged to take lead responsibility for its security by the end of 2014.
Meantime, U.S. forces are slated to withdraw completely from Iraq by the end of this year.
If those schedules hold and no new wars erupt, analysts predicted the military will confront calls from Congress to roll back troop levels even further, perhaps to levels not seen since the 2003 invasion of Iraq.
"That pressure is going to be inevitable," said Barno, a senior fellow at the Center for a New American Security, a national security think tank with close ties to the Obama administration.
There are currently about 202,000 Marines on active duty, up from 175,000 in 2007. The Army has about 569,000 soldiers on active duty, including a temporary increase of 22,000 that is already scheduled to lapse in 2013.
The permanent rollbacks will be complete by 2016 and will save $6 billion over two years. Gates said the cuts were prompted by the country's "dire fiscal situation." But he noted that the Army and Marines will still be larger - by 40,000 soldiers and 7,000 to 12,000 Marines - than when he took over as defense secretary in December 2006.
Senior military officials said they supported the troop cuts, but warned against going any deeper.
"Any significant additional budget cuts can almost only be met - keeping us whole, not hollowing us out - can only be met through substantial reductions in force structure, and that's against the national security requirements that we see in the world we're living in," Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, told reporters Thursday.
The Bush administration and Congress agreed to bolster the Marines and Army in 2007 as part of the troop surge in the Iraq war. Although large numbers of troops have since withdrawn from Iraq, many others have deployed to Afghanistan as part of the Obama administration's surge there.
Army and Marine officials both say the current size of their active-duty forces has also been necessary to provide relief after nearly a decade of war. They have sought to increase the amount of time that troops are allowed to rest at home between deployments.
Dakota L. Wood, a retired Marine lieutenant colonel, said the size of the cuts ordered by Gates were "not that big of a deal." He said the Marines and Army should be able to shrink by attrition, without resorting to forced discharges that were necessary in the mid-1990s, when the armed forces downsized drastically after the Cold War.
But he said that the need to address record federal budget deficits means that the Pentagon will face persistent pressure to do more, especially after the U.S. role in Afghanistan diminishes. Defense spending accounts for about one-fifth of the federal budget.
"It's an opening round," said Wood, a senior fellow at the Center for Strategic and Budgetary Assessments, a non-partisan policy research institute. "This requirement to get the budget house in order is going to be a real driving factor."
Thomas Donnelly, a defense and security policy analyst at the conservative American Enterprise Institute, said it was "shocking" that the Pentagon had proposed cuts in the size of its land forces while it remains embroiled in two troop-intensive wars that could remain volatile for a long time.
He said he was skeptical that the Obama administration would be able to "hand over the keys" to the Afghan government in 2014, and added that a sizeable contingent of U.S. troops might be needed in Iraq for years to come.
At the same time, he acknowledged that bipartisan concern over the federal budget deficit has undermined the Pentagon's political support base on Capitol Hill, exposing the military to the possibility of more drastic reductions.
"The politics of defense spending are very much uncertain. The libertarian right would be just as happy to get out of Afghanistan as the Nancy Pelosi-left," Donnelly said. "And now you have the conservative, shrink-the-government types. Where they'll actually come out on this thing is to be determined."