What best describes guerrilla warfare?

Guerrilla warfare is characterized by its nontraditional approach, where small, mobile groups engage in combat tactics that emphasize flexibility and surprise attacks rather than direct confrontations with larger, organized military forces. This method enables these smaller groups to use the element of surprise, often conducting ambushes and hit-and-run attacks to disrupt the enemy's operations while relying heavily on their knowledge of the local terrain. This type of warfare is often employed by groups that may not have the resources to face a conventional army in open battle, allowing them to challenge more powerful opponents effectively.

The other options describe different forms of military engagement that do not fit the essence of guerrilla warfare. Large battles with formal armies represent traditional warfare, naval engagements focus on maritime conflicts, and reliance on artillery suggests a static and heavily armed approach rather than the mobility and flexibility inherent in guerrilla tactics. Thus, nontraditional fighting with small, mobile groups is the defining feature of guerrilla warfare.