San Sim, 23
The youngest of 11 children, Sim was born in the Philippines to parents who had fled the Khmer Rouge in Cambodia. After Sept. 11, Sim decided to join the military and fight for the country that gave his family a chance to live in peace. Sim died during his third tour while on patrol in Afghanistan. He was killed two days after his son's first birthday.
Sources: Times research, Defense Department, iCasualties.org