Civil War re-enactment

Paraphrased from the latest "Reader's Digest":

My nephew, a Civil War enthusiast, thought his young son Will would enjoy seeing a Civil War reenactment. However, the booming cannons and chaos terrified the small boy. During a lull in the action my nephew finally got poor Will to calm down. It was at this moment, however, that the Confederate general shouted, "Fire at will!"