The early 1960's military airlift capability was inadequate to support a new national policy of flexible military response to aggressor action. An Air Force Specific Operational Requirement for an airlift vehicle of massive payload potential with extremely high operational reliability initiated development of the C-5 aircraft. Combat troop and cargo handling requirements for the C-5 are reviewed as they were originally defined. The eventual sequence of refinements to those requirements is characterized by continual change and improvement of requirement definition. Joint government and contractor C-5 development effort is traced through first aircraft flight, and a baseline of C-5 combat troop and cargo handling requirements is established for future comparison with the actual C-5 capabilities.