Tristan N Aitken

As a teen, Tristan Aitken raced twice in the national Soap Box Derby championships. But the Army’s high-tech fighting machines became his professional passion.

His father, Ron, said Aitken often marveled at how “ ‘they pay me to play with these things.’ It’s Star Wars for him. He loved it.”

Aitken, 31, of State College, Pa., died April 4 in Iraq when a grenade struck his Humvee.

“He was a gung-ho’er,” Ron Aitken said. “He went into Iraq saying: ‘Dad, I’m in God’s hands. Don’t worry about me.’

The father, a retired chief petty officer in the Navy Reserve, was bitter at the loss: “To lose my son for some people’s hidden agenda in an unjust war is a real tragedy.”

“My kids are Republicans, and my wife and I are Democrats,” the...