President Obama plans to overhaul the Joint Chiefs of Staff this year as he seeks to replace a handful of longtime members whose terms are coming to a close.

Obama on Tuesday nominated Marine Gen. Joseph Dunford, commandant of the Marine Corps, to succeed Army Gen. Martin Dempsey as chairman this fall. He also tapped Air Force Gen. Paul Selva, head of U.S. Transportation Command, to replace Navy Adm. James "Sandy" Winnefeld as vice chairman.

In the roles since 2011, Dempsey and Winnefeld are expected to retire after their current two-year terms end in October and August, respectively. What's more, two other members of the president's cadre of military advisers are scheduled to step down in September, including Army Gen. Raymond Odierno, chief of staff of the Army, and Navy Adm. Jonathan Greenert, chief of naval operations.

The Joint Chiefs shakeup, if approved by the Senate, may leave a mark on the last two years of Obama's presidency. In recent months alone, he consulted with his military advisers and national-security staff in authorizing U.S. military responses to a rising number of global threats, from Islamic militants in Iraq and Syria to Russian military involvement in the Ukraine.

While Dunford has the shortest tenure of any of the current service chiefs on the panel -- just 200 days -- he has years of experience in leadership roles and commanding troops in combat. He was in charge of U.S. and NATO forces in Afghanistan from 2013 to 2014, served as an assistant commandant from 2010 to 2012, and led Regimental Combat Team-5 under then-Gen. James Mattis during the 2003 invasion of Iraq.

Michael O'Hanlon, a senior fellow who specializes in national security and defense policy at the Brookings Institution, a nonpartisan research organization in Washington, D.C., praised Dunford for his combat experience, as well as his knowledge about the Pentagon's strategic shift to the Asia-Pacific region and budgetary matters.

In an email, he described the general as "very smart, very good listener, pragmatic, respectful yet hardly retreating."

Even so, O'Hanlon said the pending departure of such high-profile members of the Joint Chiefs as Odierno and Greenert are "major losses" that could impact the quality and type of military advice furnished to the president.

"There are strong people behind them but still, Odierno is sort of Mr. Army at this point in his career, and Adm. Greenert is very experienced among other things with the China relationship," he wrote. "These are major losses indeed, and there is probably a case to be made for ignoring usual rules and keeping one or both for yet another two-year term."

Obama this year will also nominate a new commandant of the Marine Corps, if Dunford is confirmed as expected. And next year do the same for Air Force Gen. Mark Welsh, chief of staff of the Air Force, and Army Gen. Frank Grass, chief of the National Guard Bureau, whose terms will expire in 2016.

The counsel from senior uniformed leaders will be all the more important in the coming period, given the president's record-low approval ratings from rank-and-file troops.

Only 15 percent of career-oriented service members approve of Obama's performance, down from 35 percent in 2009, according to a Military Times survey conducted in late 2014. By comparison, 46 percent of Americans overall approve of his job, down from 65 percent shortly after he took office in 2009, according to a Gallup poll conducted this month.

Experts credited the slide in Obama's approval ratings among those in uniform to sweeping changes to military personnel policies enacted during his tenure, such as opening more combat-related jobs to women, ending "don't ask, don't tell" and allowing gays to serve openly, and downsizing the force and laying off otherwise qualified troops due to budget constraints.

At the same time, despite more than a decade of U.S.-led wars in Iraq and Afghanistan, polls show more Americans support military intervention abroad.

Nearly two-thirds of Americans, or 63 percent, approve of the U.S. air campaign against the Islamic State in Iraq and Syria, up from 57 percent in October, according to a Pew Research Center survey conducted in February. Put another way, about twice as many people now approve of the mission than disapprove of it.

And while the public is split over the possibility of sending U.S. ground troops to the region, almost as many people now favor the idea as oppose it. About 47 percent of Americans support the idea, up from 39 percent in October, while 49 percent are against it, down from 55 percent in the fall, according to Pew.

-- Brendan McGarry can be reached at Brendan.McGarry@military.com.