About this series

Soldiers through the years have had different names for it: Soldier's heart. Shell shock. Battle fatigue. PTSD.

But the symptoms of warfare trauma have not changed: Flashbacks, nightmares, withdrawal, emotional tempests, isolation.

The number of post-traumatic stress disorder cases from the Iraq conflict is already large and expected to grow. Today, 3 1/2 years after the war began, studies show between 11 and 17 percent of those fighting have showed signs of it. And some specialists worry that the nature of this war, with its guerrilla style attacks, random killings, and exhausting need for constant vigilance, make PTSD a particularly powerful risk.

For nearly a year, the Globe has documented the consequences of a roadside bombing in Baghdad that killed Jeremy F. Regnier, 22, of Littleton, N.H., in October 2004.

This series is based on extensive interviews with the two soldiers who survived the blast when their Bradley Fighting Vehicle was attacked outside Baghdad International Airport and with the friends and family of Jeremy Regnier. It is also based on in-depth discussions with the soldiers they served with, and with the physicians who are treating the survivors today for PTSD.

Unless otherwise noted in the text, all direct quotes were either heard by a reporter or confirmed by those present when the conversation took place. When someone's thoughts or feelings are described, the source is that person.

The series also draws from military and medical records, letters, and e-mails sent from the battlefield, and reporting from New Hampshire, Ohio, Indiana, Texas, and Georgia.