Final answer:
Robert McNamara left his role as president of Ford Motor Company to become the Secretary of Defense in Kennedy's cabinet.
Step-by-step explanation:
Before taking on his role in President John F. Kennedy's cabinet, Robert McNamara gave up his position as the president of Ford Motor Company. McNamara became the Secretary of Defense, a post where he was known for advocating the administration's flexible response strategy, which included developing various military capabilities to address international conflicts and crises more effectively. The move from the automotive industry to such a high-ranking government position marked a significant career change for McNamara, as he entered the intense political stage of the 1960s.