Robert McNamara
McNamara ended the "Massive Retaliation" policy that came from the presidency of Dwight Eisenhower. Instead, McNamara put in place "flexible response" which allowed more options for defending the US. President Kennedy very much wanted to fight communist revolutions and wars to stop Soviet power from spreading, and McNamara supported this. He also played a big role in peacefully ending the Cuban Missile Crisis. He advised Kennedy to blockade Cuba and stop the Soviet Union from putting more missiles there. Kennedy agreed and their strategy worked.