What emergency action should be taken if a casualty is unconscious but breathing?

When dealing with an unconscious but breathing casualty, the appropriate action is to place them in the recovery position. This position is vital as it helps maintain an open airway, allowing the person to breathe freely. It also minimizes the risk of choking in case the individual vomits. The recovery position helps to stabilize their condition while waiting for emergency services to arrive, ensuring that their airway remains clear and that they can safely breathe without obstruction.

Other options do not effectively address the situation. Leaving the person alone could lead to further complications, and shaking them to wake up may not be safe or effective, potentially leading to injury. Performing CPR is only necessary if the individual is not breathing, which is not the case in this scenario. Thus, placing the casualty in the recovery position is the best practice to ensure their safety until professional help arrives.