Washington ? Digging deeper for help in Iraq and Afghanistan, the Army is recalling to active duty about 5,600 people who recently left the service and still have a reserve obligation.

In a new sign of the strain the insurgency in Iraq has put on the U.S. military, Army officials said Tuesday that the involuntary callups would begin in July and run through December. It is the first sizable activation of the Individual Ready Reserve since the 1991 Gulf War, though several hundred people have voluntarily returned to service since the Sept. 11, 2001, terror attacks.

Unlike members of the National Guard and Reserve, individual reservists do not perform regularly scheduled training and receive no pay unless they are called up. The Army is targeting its recall at those who recently left the service and thus have the most up-to-date skills.

“This was inevitable when it became clear that we would have to maintain significant combat forces in Iraq for a period of years,” said Dan Goure, a military analyst at the Lexington Institute, a think tank.

The Army is pinpointing certain skills in short supply, like medical specialists, military police, engineers, transportation specialists and logistics experts. Those selected for recall will be given at least 30 days’ notice to report for training, an Army statement said.

Vietnam veteran Chuck Luczynski said in an interview Tuesday that he feared his son, Matt, who is getting out of the Army after four years, will be called back to active duty as part of the individual reserves. The son returned home in March after a one-year tour in Iraq with the 101st Airborne Division, and he’s planning to start a computer programming business.

“I think that’s on everybody’s mind right now, that they took their turn and they would hope everybody took a turn so that a few don’t carry the many,” said the elder Luczynski, of Omaha, Neb.

The Army is so stretched for manpower that in April it broke a promise to some active-duty units, including the 1st Armored Division, that they would not have to serve more than 12 months in Iraq. It also has extended the tours of other units, including some in Afghanistan.

“It is a reflection of the fact that the (active-duty) military is too small for the breadth of challenges we are facing,” Goure said.

The men and women recalled from the Individual Ready Reserve will be assigned to Army Reserve and National Guard units that have been or soon will be mobilized for deployment to Iraq or Afghanistan, unless they successfully petition for exemption based on medical or other limitations.

Members of Congress were notified Tuesday of the recalls.

Those in the Individual Ready Reserve are former enlisted soldiers and officers who have some nonactive-duty military service obligation remaining, under terms they signed when they signed on but who chose not to fulfill it in the Guard or Reserve.

The Pentagon had hoped to reduce its troop levels in Iraq to about 105,000 this spring, but because of increasingly effective and deadly resistance the level has risen to about 140,000.