The history of Europe covers the peoples inhabiting Europe from prehistory to the present. During the Neolithic era and the time of the Indo-European migrations Europe saw migrations from east and southeast and the following important cultural and material exchange. The period known as classical antiquity began with the emergence of the city-states of ancient Greece. Later, the Roman Empire came to dominate the entire Mediterranean basin. The fall of the Roman Empire in AD 476 traditionally marks the start of the Middle Ages. Beginning in the 14th century a Renaissance of knowledge challenged traditional doctrines in science and theology. Simultaneously, the Protestant Reformation set up Protestant churches primarily in Germany, Scandinavia and England. After 1800, the Industrial Revolution brought prosperity to Britain and Western Europe. The main powers set up colonies in most of the Americas and Africa, and parts of Asia. In the 20th century, World War I and World War II resulted in massive numbers of deaths. The Cold War dominated European geo-politics from 1947 to 1989. Unification into a European Union moved forward after 1950, with some setbacks. Today, most countries west of Russia belong to the NATO military alliance, along with the United States and Canada.