Which fighting position allows one person to rest while the other maintains security?

The correct choice is the improved two-person fighting position. This type of position is specifically designed for two individuals to work together effectively during combat scenarios. One member can maintain a lookout and provide security, while the other can rest or prepare for any necessary actions. The layout usually allows for overlapping fields of fire and effective communication between the personnel, which enhances overall situational awareness and safety.

In tactics, this arrangement is vital as it enables combatants to sustain their operational readiness over extended periods. This mutual support system also allows for a higher defense capacity against potential threats. In contrast, the other types of positions, while useful in certain situations, do not offer the same level of cooperation needed for resting while maintaining security.

For instance, an improved one-person fighting position is primarily suited for solo use, focused on maximizing the efficiency of one individual. Positions with barriers may offer cover but do not inherently facilitate the concept of one person resting while the other is active. Lastly, a concealed fighting position focuses more on hiding the military personnel's presence rather than on collaborative security measures. Hence, the improved two-person fighting position is the most effective for the scenario described in the question.