Here's one place with plenty of job openings: the "E" Ring of the Pentagon.

In the next several months, the secretary of defense and four of the six uniformed members of the Joint Chiefs of Staff are expected to retire.

This kind of mass exodus of military brass is "virtually unheard of," said John Ullyot, a Republican strategist and former spokesman for the Senate Armed Services Committee. "It's very rare to have so many service chiefs up" all at once, he said.

"Even in peacetime this would be a lot of turnover, a lot of change for the biggest part of the discretionary budget. But in wartime it's even more complicated and needs to be done with great care to ensure that there's a smooth transition," Ullyot said.

The changes in command come as President Barack Obama faces major decision points in the Afghanistan war and prepares to joust with a new, more adversarial Congress over defense spending and his intention to lift the military's "don't ask, don't tell" policy on gays.

"This is where the president makes a lasting impact upon defense policy," said retired Army Col. and military analyst Kenneth Allard, referring to the Joint Chiefs.

Among the tasks they will carry out, "priorities clearly must respect the need for a leaner, meaner DOD, including the next wave of procurement reform" and winding down the wars in Iraq and Afghanistan, Allard added.

Obama's Hand-Picked Team

Defense Secretary Robert Gates, a Republican holdover from the Bush administration, is expected to step down in early 2011, and the guessing game about Obama's choice for a successor has been a Washington pastime for months.

Except for Air Force Chief of Staff Norton Schwartz, whose term is up in 2012, Obama will soon have his own hand-picked team at the Pentagon.

Obama recently named a new commandant of the Marine Corps, Gen. James Amos. The gruff-talking Marine is already in hot water with Adm. Michael Mullen, chairman of the Joint Chiefs, for publicly questioning the president's intention to allow gays to serve openly.

Despite Amos' remarks, which are in line with the views of his predecessor, the president is likely to look for senior officers who "understand that when the commander in chief says do it, you shut up and do it," said Heather Hurlburt, executive director of the National Security Network, a liberal defense think tank.

Mullen, who has championed an end to "don't ask, don't tell," leads the list of top military advisers who are leaving. Marine Gen. James "Hoss" Cartwright, the vice chairman, also is set to leave his post but might end up staying because he is widely viewed as the front runner for a promotion to the top spot.

Cartwright was depicted in Bob Woodward's "Obama's Wars" as the president's favorite general for his input in crafting the administration's Afghanistan policy. He had been mentioned as a possible national security adviser. But with that job filled, he could get the chairman's job.

Gen. David Petraeus, Obama's go-to guy to run the war in Afghanistan after the commander there self-destructed in Rolling Stone magazine, also is mentioned as a candidate for chairman. Some observers are skeptical though, noting that Petraeus would be the third Afghanistan commander yanked from that critical battlefield since Obama became president.

"He's too valuable to the president where he is now," said Ullyot, noting that the July deadline to begin withdrawing U.S. troops from Afghanistan is looming.

Candidates to fill the vice chairman's slot include the commander of NATO, Adm. James Stavridis; Marine Gen. James Mattis, commander of U.S. Central Command; and Army Gen. Ray Odierno, a veteran Iraq commander who now heads Joint Forces Command.

Odierno also is mentioned to replace outgoing Army Chief of Staff Gen. George Casey Jr. Another possible replacement: Army Vice Chief of Staff Peter Chiarelli, the point man on improving care for wounded warriors and fighting an epidemic of military suicides.

Also leaving is Adm. Gary Roughead, chief of naval operations. Adm. Patrick Walsh, commander of the U.S. Pacific Fleet, is among those said to have the inside track, according to Ullyot.

The next leaders of the joint chiefs "will have to be widely recognized as apolitical advisers, uninfluenced by political crosscurrents, and prepared to give their candid advice on some of the most contentious and potentially dangerous issues in foreign and defense policy," said David Barno, a retired Army three-star general who commanded U.S. and allied forces in Afghanistan in 2003.

They will have to do so, he added, "in a way that is both credible, persuasive and understandable to their masters in the White House and on the Hill who may have little or no military experience by which to judge the incoming message."

Obama "should look for people who will tell him the truth, even when he doesn't want to hear it," said Thomas Ricks, senior fellow at the Center for a New American Security. "I think Mullen has done this for him, but I am not sure he appreciates it."

Daunting Challenges

The president's next military advisers will have to face the fact that the days of spiraling defense budgets are over. Gates has called for deep spending cuts, and it will be up to them to carry them out.

Democrats aren't the only ones demanding defense cuts; some new Republican members of Congress say the Pentagon will not be exempt from spending cuts.

"The administration needs a team that will not oppose cuts to the defense budget," said Loren Thompson, a defense analyst at the Lexington Institute, a conservative think tank in Arlington, Va. "It is impossible to achieve major deficit reduction without defense doing its part, but many military leaders don't seem to grasp that they are part of the problem."

With Gates gone, it will be up to his successor to carry out the new austerity in the face of a more hawkish Republican-controlled House that will be less willing to trim defense spending.

"Obama needs a defense secretary who can insulate him from partisan attacks over national security," Thompson said. "Robert Gates has served that purpose well, but the president can't pick another Republican without offending his core supporters."

Hurlburt said the next defense secretary must command "the respect of the Pentagon, the respect of the White House and the respect of Congress and [be able to] stare down any or all of them if need be."

Thompson is among those who say "the most obvious choice" is Secretary of State Hillary Rodham Clinton. "She is tough, smart and well regarded by the troops," he said. "She understands the current state of play in U.S. strategy and learned a great deal about military programs while serving in the Senate."

Sen. Jack Reed of Rhode Island, a West Point graduate who serves on the Armed Services Committee, is reported to have turned down the job. Others on the short list to replace Gates:

• Michele Flournoy, undersecretary of defense. A defense policy wonk, who like Clinton would be the nation's first female defense secretary. But her role as an Obama campaign adviser could make her confirmation tough sledding.
• Richard Danzig, a former Navy secretary in the Clinton administration. He is now chairman of the Center for a New American Security, a Washington think tank.
• Navy Secretary Ray Mabus, a former governor of Mississippi who also served as ambassador to Saudi Arabia.
• Congressman Ike Skelton of Missouri. The chairman of the House Armed Services Committee was one of several veteran Democratic defense experts defeated in last week's election. But since he is nearly 79, it's not clear he is looking for another career.
• John Hamre. A former undersecretary of defense under Clinton, he now heads the Center for Strategic and International Studies.

Said Barno: "Filling the giant-size boots of Bob Gates will be an intimidating task, not lost on any of the prospective contenders."