The mass media tended to report on this use of the IRR as something between fraud and involuntary servitude. Makes for a better news item that way.
The U.S. Marine Corps is using its IRR (Individual Ready Reserve) troops to limit the amount of time troops spend in a combat zone. Next to the army, the marines have spent the most time in Iraq and Afghanistan. But the army, with a much larger reserve (about 140 reservists for every hundred active duty troops, compared to only 58 for the marines) has sent a larger proportion of its force to the combat zones. But three years of combat in Iraq, and five in Afghanistan, has caught up with the marines. So they are calling up 2,500 of their IRR troops. Most people in the IRR are there for four years, to finish out the eight year obligation incurred when they enlisted (usually for four years of active duty.) The marines have about 58,000 troops in the IRR, which exists for situations like this. The marines are not calling up anyone in their first year of the IRR (that is, who just got off active duty). Marines being called up will have at least five months warning, before they begin 12-18 months of active duty. The marines are also encouraging, with some success, IRR and recently retired marines to volunteer for activation.