If you usually listen to the 6 o'clock news while waiting for dinner to be served, you would tend to associate the news with dinner, and eventually the sound of the 6 o'clock news alone might cause your mouth to water even if dinner was not being prepared. this is known as

This was known as classical conditioning.
classical conditioning happen when a certain biological response is being associated a certain stimulus.
The term was first coined by a famous psychologist named Ivan Pavlov, who conducted a very similar experiment with dogs (he made the the dog's mouth to water after conditioned them to receive foods after hearing bells)

The two nation formed an alliance to define each other in case of attack