If a Master Engineer is not fleeing, a single war machine that is within 3" of him can use his Ballistic Skill and re-roll one artillery dice during the Shooting phase. This cannot be the artillery dice that determines the distance a cannonball bounces or Flame Cannon’s burst of flame moves. You must nominate which weapon, if any, will be using this special rule at the start of each Shooting phase, before any such weapons within 3" of the Master Engineer are fired. A Master Engineer cannot use this special rule and shoot with his own missile weapon in the same Shooting phase.