Which of the following is NOT one of the key battle drills?

The identification of "Scout" as the option that is not one of the key battle drills is based on how battle drills are defined and categorized within military operations. Key battle drills refer to standardized, practiced responses that soldiers can execute quickly under stress, and they typically involve essential actions in combat scenarios.

"React to contact," "Raid," and "Ambush" are all considered key battle drills. "React to contact" teaches troops the immediate actions to take when coming under fire, ensuring they can respond effectively and maintain control of the situation. A "Raid" involves a surprise attack on an enemy position with the intention of quickly gaining a tactical advantage and withdrawing. An "Ambush" is a coordinated attack designed to catch the enemy off guard, utilizing concealment and the element of surprise.

In contrast, "Scout" refers to reconnaissance operations where troops gather intelligence about enemy locations, movements, and terrain rather than executing direct combat actions or drills. Therefore, while scouting is a crucial aspect of military operations, it does not fit the definition of a key battle drill intended for immediate combat engagement.