"He talked to me in the day, which would be in the middle of his night," his father, Dan Anders, said. "He didn't sleep. He was just worried." 

There were good reasons for concern. During his six-month tour, the Taliban staged a major attack at his base, a suicide bomber had killed one of his brigade's most revered leaders, and an Afghan villager threw a fire-bomb at a vehicle he was traveling in.

  But what Anders may not have expected is that his killer would be an Afghan army soldier, one of those the U.S. military is supposed to be training to take over security of the country ahead of the withdrawal of most U.S. troops by the end of 2014.