Stretched thin by four years of war, the Army is adding three months to the standard yearlong tour for all active-duty soldiers in Iraq and Afghanistan, an extraordinary step aimed at maintaining the troop buildup in Baghdad. The change, announced Wednesday by Defense Secretary Robert Gates, is the latest blow to an all-volunteer Army that has been given ever-shorter periods of rest and retraining at home between overseas deployments. Rather than continue to shrink the at-home intervals to a point that might compromise soldiers' preparedness for combat, Gates chose to lengthen combat tours to buy time for units newly returned from battle. The longer tours will affect about 100,000 soldiers currently in Iraq and Afghanistan, plus untold thousands more who deploy later. It does not affect the Marine Corps or the National Guard or Reserve. "Our forces are stretched; there's no question about that," Gates said.