Final answer:
Charlemagne brought peace to western Europe during his reign, but it was not permanent. His empire lasted for over 40 years and united western Europe for the first time since the collapse of Roman authority.
Step-by-step explanation:
Charlemagne brought peace to western Europe during his reign, which lasted for over 40 years from 768 to 814. However, it is important to note that the peace he brought was not permanent.
During his conquests, Charlemagne waged constant wars to convert non-Christian Germans and seize loot for his followers. His vast empire eventually extended from modern France to Germany, northern Italy, and parts of northern Spain and central Europe, uniting western Europe for the first time since the collapse of Roman authority.
While Charlemagne's empire did not last beyond his reign, the concept of the Holy Roman Empire, which arose from his conquests, lasted almost exactly 1,000 years until it was permanently dismantled by Napoleon in 1806.