The Eternal Mercenary — Barry Sadler

When they flew Casey into the hospital at Nha Trang, the medics were sure he'd die. That he didn't was only the first surprise.

The second, bigger one, was that Casey had been fighting for two thousand years, ever since that day on Golgotha when he put his lance into the side of the Man on the Cross.

"Soldier, you are content with what you are. Then that you shall remain until we meet again."

Thus does Casca's journey begin, a man who cannot die, does not age, and knows no skills but those of battle.