"Well over 1 million U.S. troops have fought in the wars since Sept. 11, 2001, according to Pentagon data, approximately one-third the number of troops ever stationed in or around Vietnam during 15 years of that conflict.
"There are no front lines in Iraq: Transportation companies, military police and civil affairs soldiers face the same risk of random ambush or death by roadside bombs. The stress goes on 24 hours a day for an entire tour. Veterans of Vietnam say some of that sounds eerily familiar.
"During the 15 years of the Vietnam conflict, around 2.4 million troops served there, with perhaps another 1 million troops in surrounding countries during that time. Troop levels peaked in Vietnam in 1968 when nearly a half-million troops were there.