 Complete the following phrase:  Warfare during this 500-year period 938-1407 was characterized by a combination of amphibious and land assaults. Owing to the fragmented terrain and long coast line of the country, maneuvers by boats were favoured by most military forces who had fought in Vietnam. Small-scale coastal and border raids were frequent. Domestic violence as well as foreign incursions were equally common. It is possible that during this period that Vietnam was at its height of power, first by 