[matese]

Originally Posted by yorkietalkjilly

Just stepping in every time for a few weeks to immediately stop the activity will, over time, send a strong message with a firm "No" and backing the dog off by walking into him or, in some circumstances, clasping the back of the neck in a firm but always non-painful(!) grip and holding it in place for several long seconds to bring him up short and convey your determination that you do not intend to allow this type of behavior - period, end of sentence. In a wild pack setting, an alpha dog who is correcting a pack-member's actions will often just put their teeth over the back of the neck of that dog and hold it still for a while until the dog backs down. When you convey your correction correctly, even the most aggressive little terrier will in time begin to police himself before you have to step in but it will take persistence on your part at first. Just take extra care to never intimidate or scare him when correcting his aggressive prey-driven biting as it's not necessary and can destroy some dog's trust in their owner or trainer.

As gracielove suggested, teaching him basic ground rules for behavior will teach him impulse control by engaging him in fun and regular obedience training and can work wonders with pugnacious little dogs who occasionally lose control and go after the cat or other dogs and make that animal's life miserable. Before long, just a "No" will back him off or even just a stern look.

1000% in agreement