Some historians of times past believed that there were cycles during which demonic activity increased, and used this theory to explain various occurrences, much in the same way as today’s economic historians might explain historical events in terms of trade, productivity and other factors.
These older historians saw a rise in demonic activity accompanying such occurrences as the destruction of Jerusalem, the fall of Rome and the French Revolution, and would in all likelihood also have viewed the demonic theory at work in relation to the rise of Nazism and World War II.