After the barbarian sack of Rome in the fifth century, the seat of imperial power shifted to Constantinople, and Western Europe plunged into darkness. The next five centuries were a period of decline: in agriculture, in education, in science and the arts, in urbanization, in population. Foreign invaders swept through the continent, wreaking havoc. Crop yield was routinely low. Feudalism was established. The Plague of Justinian, thought to be smallpox, killed off half the population. Most settlements were small, with farmland and vast swaths of depopulated wilderness separating them. Trade was at an historic low. By 1000, the climate warmed from its cooling period, barbarian incursion ceased, and Europe began to emerge from the so-called Dark Ages. This crude bronze coin, a pentanummi, was struck during the reign of Justinian’s successor, Justin II, in the mid-6th century.