What is the key intervention during the Care Under Fire phase?

The key intervention during the Care Under Fire phase is the application of a tourniquet for severe bleeding. This phase is characterized by high-risk conditions where threats from hostile fire are present, necessitating immediate action to prevent life-threatening blood loss. The use of a tourniquet is critical because it can quickly and effectively control severe hemorrhage in an extremity, which is one of the leading causes of preventable death on the battlefield. This intervention prioritizes the casualty's survival while allowing the medical provider to maintain their own safety.

In this scenario, applying a bandage for minor wounds would not adequately address life-threatening injuries that can lead to rapid deterioration. Giving oral fluids is generally not feasible or safe during this phase due to the potential for further complications, such as aspiration or delayed treatment. Transporting the casualty to safety is important but typically takes place after immediate life-saving interventions, particularly in the presence of ongoing threats. Thus, controlling severe bleeding with a tourniquet is the most critical intervention in this high-risk environment.