 Through the principle of the divine right of kings, in medieval Europe for example, rulers were said to hold office by the will of God.Ancient Egypt, Imperial Japan, the Inca, the Aztecs, Tibet, Siam (now Thailand), and the Roman Empire are especially noted for redefining monarchs as "god-kings".The spread of democratic and secular ideas in Europe and North America in the 18th and 19th centuries made it increasingly difficult for monarchs to preserve this aura.