What was Dr.Ivan Pavlov's aim of his research on stimuli responses?

In classical conditioning, two unrelated stimuli are linked together to produce a learned response. In his famous experiment, Pavlov rang a bell before supplying food to a dog. Later when just the bell was rung, the dog would salivate expecting food. Thus, ringing of bell and salivation was linked in the dog which was repeatedly exposed to these two stimuli simultaneously so that it learned to respond by salivating whenever the bell was rung.