flexible response was developed so that the US did not have to resort to nuclear warfare in times of crisis

Flexible response

The flexible response was for responding to war with flexible whatevers

Flexible Response was the use of conventional forces and weapons as an alternative to nuclear war.

President Kennedy's Flexible Response was initiated to provide the United States with various means of response to aggression, not limited to nuclear attacks. As a result, his response to Vietnam was to send additional advisors, increase our military aid to the South Vietnam government and institute the disastrous Strategic Hamlet Program.