Which of the following best describes the action of ambush?

The action of ambush is best described as a surprise attack from a concealed position because it relies on stealth, preparation, and the element of surprise to effectively engage an adversary. In an ambush, troops often take advantage of natural terrain and obstacles to hide their presence until the right moment to strike. This tactic maximizes the effectiveness of the attackers while minimizing the chance for the target to respond effectively.

Ambushes are typically used not just for direct confrontation, but strategically to catch the enemy off guard, disrupt their movements, and create conditions favorable to the attacking force. Other options do not convey the essence of an ambush; they either suggest open combat scenarios, fortified positions, or retreats, which do not align with the stealth and surprise that define ambush tactics.