The United States Marine Corps is set to shed more than 20,000 active duty positions in the coming years and have already commenced a process meant to force some senior officers into an early retirement.

The Marines are on course to cut around 4,000 positions a year through 2017, decreasing the total number of Marines to 182,100 from its peak last year of 202,100, according to a major scale-down order that was quietly issued last year.

The reduction in forces could leave the elite fighting force underprepared to battle multiple regional threats, particularly those in the Middle East, according to military experts.

The impending cuts are independent of the $1.2 trillion in mandatory cuts, otherwise known as sequestration, which will take place next month if Congress fails to reach a preventative deal.

"The effect will be that there will not be sufficient Marines available to both be ‘America’s 9-1-1 force’ and to be ready for sustained ground combat," said Steven Bucci, a former deputy assistant secretary of defense who warned that the decreased number of Marines will leave the force overstretched.

"Right now, the Marines are trying to go back to the role of floating about on the three ship Amphibious Readiness Group (ARG) missions forward deployed around the world," Bucci said, referring to a joint Navy and Marine unit that performs sea-to-shore missions. "There was no ARG available to respond to Benghazi [terror attacks] because the Marines have had so many combat units fighting elsewhere."

"Cuts will prohibit [the Marines] from returning to this key role," said Bucci, director of the Allison Center for Foreign Policy Studies at the Heritage Foundation.

A spokesperson in the Marines’ Manpower and Reserve Affairs office said that the corps typically "transitions" 30,000-35,000 Marines per year, "so we are only talking about 5,000 more per year on top of that."

There are currently 195,000 active duty members, according to the official.

"In order to keep faith with our Marines, we are looking to maximize voluntary measures," the spokesperson said. "As such, several force-shaping authorities are available to us and we are offering them to Marines—in a targeted fashion."

As the Army carries out a similarly massive drawdown in forces, the Marines are being forced to enter combat roles for which they are not primarily suited, said Thomas Donnelly, a former policy group director for the House Armed Services Committee.

The Army began discharging and reassigning 60,000 soldiers, according to the Daily News of Jacksonville, N.C.

Army leaders were informed the Army is "fundamentally" altering its structure and that "some fully qualified soldiers will be denied re-enlistment," according to an Army Times report.

"The problem will come if there's a need to reverse the current retreat in the Middle East, the wars most likely to demand long-term, larger-scale land forces," explained Donnelly, who is currently a fellow at the American Enterprise Institute.

"In a few years, the Army will be worse off than it was prior to 9/11 and less able—though the most natural and most able long-war force—to sustain that sort of operation," he said. "Under those circumstances the Marines will get sucked back into the sort of mission they've had in Anbar and Helmand [provinces in Iraq and Afghanistan] of late."

The Marines have already announced the formation of several voluntary and coercive commissions aimed at paring down the force.

Selective early retirement boards, for example, will force at least 200 lieutenant colonels out of the service, according to unclassified announcements.

"Officers selected for early retirement have been personally notified of their selection by the first marine three-star general officer in their chain of command," states one announcement that was issued last week.

Another forced retirement notice from last year acknowledges that the Marines are under-resourced.

"As we move into an environment of reduced resources and reduced end strength, we face tough decisions that will affect the marines who have been dedicated to service throughout the recent decades of peace and war," the announcement states. "For a second time, our corps must face the tough decision of how to manage the kind of surplus in senior field grade officers we have today."

Other officers are being forced to compete for scant positions, according to another announcement issued in November.

An "officer retention board" will determine which officers can remain on active duty, according to the notice.

"Career designation is a force shaping tool that allows for the management of the officer population by retaining the best qualified officers from each year group," the notice states. "Those selected for career designation are offered the opportunity to remain on active duty."

"Officers will be considered for career designation in five competitive categories in the military occupational specialties (MOS) listed," including proficiency in combat arms and other areas.

Several voluntary programs additionally offer enlisted members an early retirement. The programs are meant to quickly pare down the force and save costs in a tight budgetary environment.

The Marines could be forced to cut an additional number of enlisted members should the sequestration take effect later this year, leaving the force even weaker, experts said.

"Sequestration would badly hurt USMC readiness," said Heritage’s Bucci. "Now that the president seems to have put the blame on the Republicans, the other [Joint Chiefs of Staff] have finally started to fess up to the truth: These cuts will make the military hollow."

"They will not have enough people, trainings, or equipment to provide for the common defense," Bucci said.