A friend had two dacsies - OK, they're not corgs, but are similar sized dogs - who went for a burglar who broke into her house. He cut and ran, with the dogs after him. He tried to climb over the 6' fence at the back; the dogs lept up as one, grabbed onto his feet - one for each, and literally hung there until the cops arrived.
Not bad, eh, for "small, non-guarding" dogs.