Why American 'Soldier of Christ' Is Taking on ISIS

He calls himself a "Soldier of Christ," and he's back in Iraq battling ISIS on the front lines.

The man, identified only as Brett, is a 28-year-old U.S. Army Iraq war veteran. For the safety of his family, he's requested that his last name remain unknown.

Brett returned to Iraq six months ago to join a Christian militia fighting ISIS. He's involved in a battle near Mosul.

"I may not know them before, but they're my people -- the Assyrian Christians of this world -- they're indigenous to this part of the world," Brett said. "People are hell-bent on erasing them in the history."

"People ask me, 'Why you?' I come back, and I say, 'Why not? Why just me? Where's everyone else at?'" he told ABC News.

"Jesus says, you know, 'What you do unto the least of them, you do unto me,'" he added. "I take that very seriously."

Brett said he has a price on his head but says it's in God's hands and God's will. He believes God has equipped him with many tools to fight ISIS.