Which of the following is an indicator for a defensive operation mode?

A defensive operation mode is characterized by a strategy focused on protecting exposure and preventing the spread of fire, often employed when conditions are hazardous for personnel. The presence of imminent collapse is a critical indicator for adopting this mode. When firefighters assess the risk of structural failure, they must prioritize the safety of their own teams, as well as any civilians in the vicinity. If the structure poses an immediate risk of collapse, engagement in an offensive strategy could result in unnecessary danger to responders, thereby making a defensive posture more appropriate.

Indicator elements such as a command vehicle or the availability of backup units can enhance operations but do not, on their own, suggest a defensive strategy. Moreover, the successful evacuation of occupants is a crucial measure of incident management but may not indicate the need for a defensive operation; instead, it signifies that life safety efforts have succeeded. In contrast, the danger of imminent collapse directly signals that a defensive approach is necessary to safeguard personnel and manage scene safety while protecting surrounding areas from fire spread.