As a result of the constant attacks by the Vikings and other nomads, the governments of Europe were constantly under attack. Communities did not feel that their governments were providing adequate protection for them against outsiders. The economies of Western Europe were in shambles, and trade routes were disrupted.
As the monarchs of central governments lost power, a new type of government evolved called Feudalism. Feudalism began in France around 900 A.D., and spread throughout the remainder of Europe within 150 years.
Whoever wants to reach a distant goal must take many small steps.
Spiral staircases in medieval castles are running clockwise. This is because all knights used to be right-handed. This insured that knights running down the stars had the advantage over knights running up the stairs to invade.