Which of the following is NOT a category of reconnaissance missions?

The correct choice identifies "Engagement" as not being a category of reconnaissance missions. Reconnaissance missions are typically categorized into three main types: route, zone, and area reconnaissance.

Route reconnaissance involves gathering information about a specific route or path, allowing units to assess its suitability for passage or to identify potential enemy positions along the way. Zone reconnaissance covers a specific area to collect information regarding the enemy, terrain, and any other relevant details. Area reconnaissance focuses on a broader section to gather data that supports planning and operational effectiveness.

In contrast, an engagement refers more to direct combat or military actions aimed at actively confronting enemy forces rather than collecting information about them. Thus, "Engagement" does not fit within the standard categories of reconnaissance missions, making it the correct answer in this context.