Colonialism is a phenomenon that has occurred throughout human history across the world. Colonies were established by many prominent ancient and medieval civilizations, such as the Phoenicians, the Babylonians, the Persians, the Greeks, the Romans, the Han Chinese, and the Arabs, among others. The High Middle Ages saw a variety of European civilizations moving west, north, east, and south out of their continent. The Crusader states in the Levant exemplify some colonial features similar to those of ancient colonies.

The beginning of the "Age of Discovery" around 1418 marked a new phase of European colonialism led by the Portuguese, who became increasingly expansionist following the conquest of Ceuta in 1415. Portugal aimed to control navigation routes through the Strait of Gibraltar, to spread Christianity, to amass wealth and plunder, and to suppress predation on Portuguese populations by Muslim Barbary pirates, who operated as part of a long-running African slave trade that the Portuguese would soon reverse and surpass. Around 1450, the Portuguese developed a lighter ship—the caravel—based on North African fishing boats. Caravels could sail further and faster than previous vessels, A companion to the PBS Series The Genius That Was China were highly maneuverable, and had the capability of sailing into the wind.

Enabled by new maritime technology, and with the added incentive to find an alternative "Silk Road" after the Ottoman conquest of Constantinople effectively closed profitable trade routes between Asia and Europe in 1453, early European exploration of Africa was followed by the Spanish exploration of the Americas, further exploration along the coasts of Africa, and explorations of West Asia (also known as the Middle East), South Asia, and East Asia.

The conquest of the Canary Islands by the Crown of Castile, from 1402 to 1496, was an early instance of European settler colonialism in Africa. In 1462 the Portuguese established the first European settlement in the tropics by peopling the previously uninhabited Cape Verde archipelago, which thereafter became a site of Jewish exile during the height of the Portuguese and Spanish Inquisitions in the 1490s; the Portuguese soon also brought slaves from the West African coast. Because of the economics of plantations, especially sugar, much European colonial expansion and slavery would remain linked into the 19th century. The use of exile to penal colonies would also continue.

The European "discovery" of the New World (as named by Amerigo Vespucci in 1503) opened another colonial chapter, beginning with the colonization of the Caribbean in 1493 with Hispaniola (later to become Haiti and the Dominican Republic). The Portuguese and Spanish Empires were the first trans-oceanic global empires: they were the first to stretch across different continents (discounting Eurasian empires and those with land in Africa along the Mediterranean), covering vast territories around the globe. Between 1580 and 1640, the Portuguese and Spanish Empires were both ruled by the Spanish monarchs in personal union. During the late 16th and 17th centuries, England, France, and the Dutch Republic also established their own overseas empires, each in direct competition with the other European expansionists. Meanwhile the Tsardom of Russia expanded overland: Russian Central Asian and North Asian colonies eventually extended to Alaska and California.

The end of the 18th and mid-19th century saw the first era of decolonization, when most of the European colonies in the Americas, notably those of Spain, New France, and the Thirteen Colonies, gained their independence from their respective metropoles. The Kingdom of Great Britain (uniting Scotland and England), France, Portugal, and the Dutch turned their attention to the Old World, particularly South Asia and Southeast Asia, where coastal enclaves had already been established.

In the 19th century, the Second Industrial Revolution led to what has been termed the era of New Imperialism, when the pace of colonization rapidly accelerated, the height of which was the Scramble for Africa, in which Belgium, Germany, and Italy also participated. The newly westernized Empire of Japan established the Japanese colonial empire in eastern Asia (notably Taiwan, Korea, and Manchukuo) from the late 19th century. Nazi Germany pursued the Lebensraum concept of settler colonialism in Eastern Europe, and Fascist Italy pursued colonialism in Africa. All three are viewed as causes of World War II.

There were deadly battles between colonizing states and revolutions in colonized areas, shaping areas of control and establishing independent nations. During the 20th century, the colonies of the defeated Central Powers of World War I were distributed amongst the victors as mandates, but it was not until after the end of World War II that the second phase of decolonization began in earnest.

Periodization

Some commentators identify three waves of European colonialism.

The two main countries in the first wave of European colonialism were Portugal and Spain.Thomas Benjamin, ed., Encyclopedia of Western Colonialism Since 1450 (2006) 1: xiv–xvi. The Portuguese started the long age of European colonization with the conquest of Ceuta, Morocco in 1415, and the conquest and discovery of other African territories and islands, this would also start the movement known as the Age of Discoveries. The Spanish and Portuguese launched the colonization of the Americas, basing their territorial claims on the Treaty of Tordesillas of 1494. This treaty demarcated the respective spheres of influence of Spain and Portugal.Gilmartin, et al. p. 115

The expansion achieved by Spain and Portugal caught the attention of Britain, France, and the Netherlands.Jonathan Hart, Representing the New World: the English and French uses of the Example of Spain (2001). pp 85–86. The entrance of these three powers into the Caribbean and North America perpetuated European colonialism in these regions.Gilmartin, M. (2009). Colonialism/Imperialism. In Key concepts in political geography London: SAGE pp. 115–123.

The second wave of European colonialism commenced with Britain's involvement in Asia in support of the British East India Company; other countries such as France, Portugal and the Netherlands also had involvement in European expansion in Asia.Gilmartin, et al. p. 115Tonio Andrade, "Beyond Guns, Germs, and Steel: European Expansion and Maritime Asia, 1400–1750." Journal of Early Modern History 14.1–2 (2010): 165–186.

The third wave ("New Imperialism") consisted of the Scramble for Africa regulated by the terms of the Berlin Conference of 1884–1885. The conference effectively divided Africa among the European powers. Vast regions of Africa came under the sway of Britain, France, Germany, Portugal, Belgium, Italy and Spain.George Shepperson, "The Centennial of the West African Conference of Berlin, 1884–1885." Phylon 46.1 (1985): 37–48.Peter J. Cain, and Anthony G. Hopkins, "Gentlemanly capitalism and British expansion overseas II: New imperialism, 1850‐1945." Economic History Review 40.1 (1987): 1–26. online

Gilmartin argues that these three waves of colonialism were linked to capitalism. The first wave of European expansion involved exploring the world to find new revenue and perpetuating European feudalism. The second wave focused on developing the mercantile capitalism system and the manufacturing industry in Europe. The last wave of European colonialism solidified all capitalistic endeavors by providing new markets and raw materials.Gilmartin, et al. pp. 115–16

As a result of these waves of European colonial expansion, only thirteen present-day independent countries escaped formal colonization by European powers: Afghanistan, Bhutan, Iran, Japan, Liberia, Mongolia, Nepal, China, North Korea, Saudi Arabia, South Korea, Thailand, and Turkey as well as North Yemen.Marcin Solarz, The Language of Global Development. A Misleading Geography. (2014), p. 18

Colonialism in ancient times (3200 BC – 7th century AD)

Colonialism in antiquity was primarily characterized by the establishment of settlements and outposts by expanding civilizations for trade, agriculture, and military advantage. In the Mediterranean, the Phoenicians developed a vast network of maritime trading colonies, most notably Carthage in North Africa, which allowed them to dominate commerce across the region. From the 8th to 6th centuries BC, the ancient Greeks founded hundreds of colonies (apoikiai) across the Mediterranean and Black Sea coasts to alleviate overpopulation, secure arable land, and expand trade, profoundly spreading Hellenic culture.

The Roman Republic and later the Roman Empire utilized colonization as a tool of military and political integration. Roman colonies (coloniae) were often established to secure newly conquered territories and reward military veterans with land, particularly in North Africa, which became a vital agricultural hub for the empire. Meanwhile, in East Asia, the Han dynasty of China expanded its influence by establishing the Four Commanderies of Han in the northern Korean peninsula during the 2nd century BC. These served as administrative and cultural outposts to project imperial power and control regional trade routes.

Portuguese and Spanish colonial hegemony: the Americas (15th century–1770)

European colonization of both Eastern and Western Hemispheres has its roots in Portuguese exploration. There were financial and religious motives behind this exploration. By finding the source of the lucrative spice trade, the Portuguese could reap its profits for themselves. They would also be able to probe the existence of the fabled Christian kingdom of Prester John, with an eye to encircling the Islamic Ottoman Empire, itself gaining territories and colonies in Eastern Europe. The first foothold outside of Europe was gained with the conquest of Ceuta in 1415. During the 15th century, Portuguese sailors discovered the Atlantic islands of Madeira, Azores, and Cape Verde, which were duly populated, and pressed progressively further along the west African coast until Bartolomeu Dias demonstrated it was possible to sail around Africa by rounding the Cape of Good Hope in 1488, paving the way for Vasco da Gama to reach India in 1498.Charles R. Boxer, The Portuguese Seaborne Empire 1415–1825 (1969).

Portuguese successes led to Spanish financing of a mission by Christopher Columbus in 1492 to explore an alternative route to Asia, by sailing west. When Columbus eventually made landfall in the Caribbean Antilles he believed he had reached the coast of India, and that the people he encountered there were Indians with red skin. This is why Native Americans have been called Indians or red-Indians. In truth, Columbus had arrived on a continent that was new to the Europeans, the Americas. After Columbus' first trips, competing Spanish and Portuguese claims to new territories and sea routes were solved with the Treaty of Tordesillas in 1494, which divided the world outside of Europe in two areas of trade and exploration, between the Iberian kingdoms of Castile and Portugal along a north-south meridian, 370 leagues west of Cape Verde. According to this international agreement, the larger part of the Americas and the Pacific Ocean were open to Spanish exploration and colonization, while Africa, the Indian Ocean, and most of Asia were assigned to Portugal.Lyle N. McAlister, Spain and Portugal in the New World, 1492–1700 (1984).