Between 1945 and 1960, three dozen new states in Asia and Africa achieved autonomy or outright independence from their European colonial rulers. There was no one process of decolonization. In some areas, it was peaceful, and orderly. In many others, independence was achieved only after a protracted revolution. A few newly independent countries acquired stable governments almost immediately; others were ruled by dictators or military juntas for decades, or endured long civil wars. Some European governments welcomed a new relationship with their former colonies; others contested decolonization militarily. The process of decolonization coincided with the new Cold War between the Soviet Union and the United States, and with the early development of the new United Nations. Decolonization was often affected by superpower competition, and had a definite impact on the evolution of that competition. It also significantly changed the pattern of international relations in a more general sense. The creation of so many new countries, some of which occupied strategic locations, others of which possessed significant natural resources, and most of which were desperately poor, altered the composition of the United Nations and political complexity of every region of the globe.

In the mid to late 19th century, the European powers colonized much of Africa and Southeast Asia. During the decades of imperialism, the industrializing powers of Europe viewed the African and Asian continents as reservoirs of raw materials, labor, and territory for future settlement. In most cases, however, significant development and European settlement in these colonies was sporadic. However, the colonies were exploited, sometimes brutally, for natural and labor resources, and sometimes even for military conscripts. In addition, the introduction of colonial rule drew arbitrary natural boundaries where none had existed before, dividing ethnic and linguistic groups and natural features, and laying the foundation for the creation of numerous states lacking geographic, linguistic, ethnic, or political affinity.

During World War II Japan, itself a significant imperial power, drove the European powers out of Asia. After the Japanese surrender in 1945, local nationalist movements in the former Asian colonies campaigned for independence rather than a return to European colonial rule. In many cases, as in Indonesia and French Indochina, these nationalists had been guerrillas fighting the Japanese after European surrenders, or were former members of colonial military establishments. These independence movements often appealed to the United States Government for support.

While the United States generally supported the concept of national self-determination, it also had strong ties to its European allies, who had imperial claims on their former colonies. The Cold War only served to complicate the U.S. position, as U.S. support for decolonization was offset by American concern over communist expansion and Soviet strategic ambitions in Europe. Several of the NATO allies asserted that their colonial possessions provided them with economic and military strength that would otherwise be lost to the alliance. Nearly all of the United States' European allies believed that after their recovery from World War II their colonies would finally provide the combination of raw materials and protected markets for finished goods that would cement the colonies to Europe. Whether or not this was the case, the alternative of allowing the colonies to slip away, perhaps into the United States' economic sphere or that of another power, was unappealing to every European government interested in postwar stability. Although the U.S. Government did not force the issue, it encouraged the European imperial powers to negotiate an early withdrawal from their overseas colonies. The United States granted independence to the Philippines in 1946.

However, as the Cold War competition with the Soviet Union came to dominate U.S. foreign policy concerns in the late 1940s and 1950s, the Truman and Eisenhower Administrations grew increasingly concerned that as the European powers lost their colonies or granted them independence, Soviet-supported communist parties might achieve power in the new states. This might serve to shift the international balance of power in favor of the Soviet Union and remove access to economic resources from U.S. allies. Events such as the Indonesian struggle for independence from the Netherlands (1945-50), the Vietnamese war against France (1945-54), and the nationalist and professed socialist takeovers of Egypt (1952) and Iran (1951) served to reinforce such fears, even if new governments did not directly link themselves to the Soviet Union. Thus, the United States used aid packages, technical assistance and sometimes even military intervention to encourage newly independent nations in the Third World to adopt governments that aligned with the West. The Soviet Union deployed similar tactics in an effort to encourage new nations to join the communist bloc, and attempted to convince newly decolonized countries that communism was an intrinsically non-imperialist economic and political ideology. Many of the new nations resisted the pressure to be drawn into the Cold War, joined in the "nonaligned movement," which formed after the Bandung conference of 1955, and focused on internal development.

The newly independent nations that emerged in the 1950s and the 1960s became an important factor in changing the balance of power within the United Nations. In 1946, there were 35 member states in the United Nations; as the newly independent nations of the "third world" joined the organization, by 1970 membership had swelled to 127. These new member states had a few characteristics in common; they were non-white, with developing economies, facing internal problems that were the result of their colonial past, which sometimes put them at odds with European countries and made them suspicious of European-style governmental structures, political ideas, and economic institutions. These countries also became vocal advocates of continuing decolonization, with the result that the UN Assembly was often ahead of the Security Council on issues of self-governance and decolonization. The new nations pushed the UN toward accepting resolutions for independence for colonial states and creating a special committee on colonialism, demonstrating that even though some nations continued to struggle for independence, in the eyes of the international community, the colonial era was ending.

Decolonization and the emergence of independent nations in Asia and Africa were a result of various factors such as nationalist movements, World War II, and the changing global political landscape. These events and developments played a crucial role in reshaping the world order and granting independence to many countries in these regions.

Nationalist Movements:
1. Rise of Nationalist Sentiments: In the early 20th century, nationalist movements began to gain momentum in Asia and Africa. People in these regions started demanding self-rule and freedom from colonial powers.
2. Influence of Leaders: Influential leaders such as Mahatma Gandhi in India, Ho Chi Minh in Vietnam, and Kwame Nkrumah in Ghana emerged during this period. They inspired and mobilized the masses to fight for independence.
3. Non-violent Resistance: Non-violent methods such as civil disobedience, boycotts, and protests were employed by these nationalist leaders and their followers to challenge colonial rule.

World War II:
1. Weakening Colonial Powers: World War II severely weakened colonial powers such as Britain, France, and Japan. The war disrupted their economies and drained their resources, making it difficult for them to maintain control over their colonies.
2. Shift in Global Power: The war also led to a shift in global power dynamics. The defeat of the Axis powers (Germany, Italy, and Japan) and the rise of the United States and the Soviet Union as superpowers created an environment conducive to decolonization. The newly emerged superpowers supported the aspirations of colonized nations for self-determination.

Changing Global Political Landscape:
1. United Nations: The establishment of the United Nations in 1945 provided a platform for colonies to voice their grievances and seek support for independence. The UN's principles of self-determination and decolonization put pressure on colonial powers to grant independence to their colonies.
2. Cold War Politics: During the Cold War, the United States and the Soviet Union competed for influence in the newly independent nations. Both superpowers supported anti-colonial movements as a means to expand their sphere of influence.

In conclusion, decolonization and the emergence of independent nations in Asia and Africa were the result of nationalist movements, the impact of World War II, and the changing global political landscape. These factors created an environment where colonial powers were no longer able to maintain control over their colonies, leading to the granting of independence to many countries in these regions.