This will be the marines' first involuntary recall since the early days of the US-led "war on terror".

Up to 2,500 soldiers will be brought back at a time, and there is no cap on the total number who may be forced back into service as the military helps fight the "war on terror". The call-ups will begin in the next several months.

The number of soldiers in Iraq has climbed back to 138,000 - the prevailing number for much of last year.

Troop levels had been declining this year, to a low of about 127,000, amid growing calls from congress and the public for a phased withdrawal. Increasing violence in Baghdad has led military leaders to increase the US presence there.

This is the first time the marines have had to use the involuntary recall since the beginning of the Iraq combat. The army, meanwhile, has issued orders recalling about 10,000 soldiers so far, but many of those may be granted exemptions.

Forthcoming deployments

Marine Colonel Guy A Stratton, head of the manpower mobilisation section, estimated that there is a current shortfall of about 1,200 marines needed to fill positions in forthcoming deployments.

Some of the military needs, he said, include engineers, intelligence, military police and communications.

As of Tuesday, nearly 22,000 of the 138,000 soldiers in Iraq were marines.

Of the 138,000 US troops in Iraq,
nearly 22,000 are marines

The call-up will affect marines in the Individual Ready Reserve, a segment of the reserves that consists mainly of those who have left active duty but still have time remaining on their eight-year military obligations.

Generally, marines enlist for four years, then serve the other four years either in the regular reserves, where they are paid and train periodically, or in the Individual Ready Reserve. Marines in the IRR are obliged to report only one day a year but can be involuntarily recalled to active duty.

To date, about 5,000 army IRR soldiers have mobilised, and about 2,200 of those are currently serving, according to Lieutenant-Colonel Bryan Hilferty, an army spokesman. Of those 2,200, about 16%, are volunteers, he said. A typical army enlistment obligation is also for eight years.

According to Stratton, there are about 59,000 marines in the IRR, but the Marine Corps has decided to exempt from the call-up those who are either in their first year or last year of the reserve status. As a result, the pool of available marines is about 35,000.

Five-month preparation

The deployments can last up to two years, but on average would be 12 to 18 months, Stratton said. Each marine who is being recalled will get five months to prepare before having to report.

George Bush authorised the recall on July 26. It is the first such recall since early 2003, when about 2,000 marines were involuntarily activated for the initial ground war in Iraq.

"Since this is going to be a long war," Stratton said. "We thought it was judicious and prudent at this time to be able to use a relatively small portion of those marines to help us augment our units."