Advanced Trauma Life Support (ATLS) provides a systematic, reproducible approach to the evaluation and management of the multiply-injured patient. The core principle of ATLS is 'treat first what kills first,' prioritizing life threats in the order they are most likely to cause death. The primary survey follows the ABCDE mnemonic performed simultaneously with resuscitation: A (Airway with cervical spine protection) — assess patency, look for obstruction, manage with chin lift/jaw thrust maintaining C-spine immobilization, definitive airway if GCS ≤8 or inability to maintain airway; B (Breathing and ventilation) — expose chest, assess bilateral chest rise, auscultate bilateral breath sounds, identify and treat tension pneumothorax, open pneumothorax, and massive hemothorax; C (Circulation with hemorrhage control) — assess pulse quality, apply direct pressure to external hemorrhage, establish large-bore IV access, initiate volume resuscitation with permissive hypotension strategy (target SBP 80-90 mmHg in penetrating trauma), activate massive transfusion protocol for class III-IV shock; D (Disability) — GCS calculation, pupil assessment, lateralizing signs, glucose check; E (Exposure/Environmental control) — fully undress, log roll for posterior exam, prevent hypothermia. Adjuncts to the primary survey include...