Washington ? The Marine Corps last week announced plans for involuntary call-ups of Marine reservists to serve in Iraq and Afghanistan. Here’s some background:

Who’s getting called up and why?

Those who stand to be summoned are Marines who recently have completed four years of active duty and are serving the remaining four years of their eight-year service commitment in a reserve program known as the “individual ready reserve.”

Do all Marines go from active duty to the individual ready reserve?

No. Some join reserve units. Some remain attached as reservists to active duty units. And about 59,000 opted to join the individual ready reserve. They are not attached to either reserve or active duty units, but are available as individuals to volunteer or be called up for duty in other units that have vacancies.

How many of those will be called up?

The Marines foresee 1,200 jobs that may need to be filled on an involuntary basis. The call-up guidelines allow commanders to summon up to 2,500 Marines, but allow them to subsequently call up additional groups of 2,500.

So some volunteer for this duty? Why?

Yes. The Marines regularly post newly created jobs or jobs that have become vacant because of casualties or discharges and encourage members of the Individual Ready Reserve to volunteer. Of course, they are paid for the duty.

Why not fill all the openings with volunteers then?

The Marine Corps would prefer to do that. But the number of volunteers have been declining over time, and the commitment of troops in Iraq and Afghanistan has remained constant. So commanders see a time when they have openings near the front lines that have to be filled and no Marines available to fill them.

The Pentagon keeps saying they’re meeting their recruiting goals. So how can there be a shortage of Marines?

The Marines have been meeting their recruiting goals. (The Army missed its goal last year; the National Guard and Army and Navy reserves are struggling this year). However, when a unit is serving in combat and Marines are killed or wounded, commanders can’t fill those jobs by simply moving Marines from other units, because that would create new vacancies. Instead, they call for help from reserves. Up until now, that call has been answered – by volunteers.

Weren’t the number of troops in Iraq supposed to go down this year?

Yes. Ever since early 2005, top commanders have predicted “substantial reductions” in the numbers of U.S. forces would occur in 2006. President Bush held out a similar hope in his State of the Union speech in January. But worsening violence has prevented commanders from going ahead with withdrawals.

How many troops do we have over there now?

As of last week, there were 138,000 U.S. troops in Iraq, including about 22,000 Marines.

The Bush administration talks about the all-volunteer force. Is the force in Iraq all volunteers?

They all voluntarily joined the military. But, as in the case of the Marines’ individual ready reserve, many had little or no choice about going to Iraq.

How many others were given no choice?

It’s difficult to say for sure. The Army tapped its individual ready reserve in 2004, mobilizing about 5,000 inactive soldiers. About 2,200 Army ready reservists continue to serve, about 1,850 of them involuntarily. In addition, many military units have been held in Iraq beyond their scheduled tours. While the Pentagon could not provide exact numbers of troops affected by such orders, there were more than 13,000 at the end of last year.