Wars of national liberation
Legal issues: International law generally holds that a people with a legal right to self-determination are entitled to wage wars of national liberation. While Western states tend to view these wars as civil wars, Third World and communist states tend to view them as international wars. This difference in classification leads to varying perceptions of which laws of war apply in such situations. However, there is general agreement among all states today in principle that the use of force to frustrate a people's legal right to self-determination is unlawful.

Strategies and tactics: Wars of national liberation are usually fought using guerrilla warfare. The main purpose of these tactics is to increase the cost of the anti-guerrilla forces past the point where such forces are willing to bear. Wars of national liberation generally depend on widespread public support, with ordinary civilians providing crucial support. Finally, wars of national liberation are often embedded in a larger context of great power politics and are often proxy wars.
These strategies explain why they are quite successful against foreign regimes and quite unsuccessful against indigenous regimes. Foreign regimes usually have a threshold beyond which they would prefer to go home rather than to fight the war. By contrast, an indigenous regime has no place to which they can retreat, and will fight much harder because of the lack of alternatives. Moreover, foreign regimes usually have fewer active supporters in the theater, and those that exist can often be easily identified, making it possible for guerrilla armies to identify their targets. By contrast, indigenous regimes often have much more popular support, and their supporters are often not easily recognized as such, making it much harder to conduct operations against them without also causing harm to neutral parties.

History: 

Decolonization period: The Haitian Revolution (1791-1804) can be considered to be one of the first wars of national liberation. It pitted self-liberated slaves against Imperial France, coming about during a period in history where interconnected movements such as the American and French Revolutions had caused a rise of national consciousness in the Atlantic world. At the same time during the Spanish American wars of independence (1808-1833), the patriots launched a series of complex wars of independence against the royalists, which resulted in the formation of new Latin American states. The Siege of Patras (1821) led to the Greek War of Independence, ending Ottoman domination in the establishment of the Kingdom of Greece. The Easter Rising (1916) in Dublin eventually led to the Irish War of Independence (1919-1921), ending in the establishment of the Irish Free State. In the aftermath of World War I and the 1917 Russian Revolution the Bolsheviks unsuccessfully fought a number of independence movements until Finland, Estonia, Latvia, Lithuania, and Poland gained independence. The Ukrainian People's Republic fought its war of independence (1917-1921), which resulted in being absorbed into a Soviet republic. Following the defeat of the Ottoman Empire, the Turkish National Movement fought a series of campaigns in the war of independence (1919-1922), which resulted in the subsequent withdrawal of Allied forces and establishment of the Republic of Turkey. The Indonesian War of Independence (1945-1949) followed with the Liberation of Irian Jaya (1960-1962), the First Indochina War (1946–54), Vietnam War (1959–75), Bangladesh Liberation War (1971) and the Algerian War (1954–62) were all considered national liberation wars by the rebelling sides of the conflicts. The African National Congress (ANC)'s struggle against the apartheid regime is also another example. Most of these rebellions were in part supported by the Soviet Union. Since the  Russian Revolution the revolutionary objectives of communism and socialism were shared by many anticolonialist leaders, thus explaining the objective alliance between anticolonialist forces and Marxism. The concept of "imperialism" itself had been theorized in Lenin's 1916 book, Imperialism, the Highest Stage of Capitalism. For example, Ho Chi Minh — who founded the Viet-Minh in 1941 and declared the independence of Vietnam on September 2, 1945, following the 1945 August Revolution — was a founding member of the French Communist Party (PCF) in 1921. In January 1961, over three years before the Gulf of Tonkin incident which would mark the United States government's increased involvement in the Vietnam War, Soviet premier Nikita Khrushchev would pledge support for "wars of national liberation" throughout the world. In the same decade, Cuba, led by Fidel Castro, would support national liberation movements in Angola and Mozambique. The Portuguese colonial wars finally led to the recognition of Angola, Mozambique and Guinea-Bissau as independent states in 1975, following the April Carnation Revolution. The 1991 breakup of Yugoslavia led to fewer wars of independence in part of the Yugoslav Wars, including the Ten-Day War and the Croatian War of Independence.

Ongoing wars defined as national liberation conflicts: The Palestine Liberation Organization (PLO) is a national liberation movement, meaning that it holds official recognition of its legal status as such. Other national liberation movements in the OAU at that time included the African National Congress (ANC) and Pan Africanist Congress of Azania (PAC). It is the only non-African national liberation movement to hold observer status in the OAU, and was one of the first national liberation movements granted permanent observer status by the United Nations General Assembly pursuant to a 1974 resolution. The PLO also participates in UN Security Council debates; since 1988, it has represented the Palestinian people at the UN under the name "Palestine".
The following current conflicts have sometimes also been characterized as wars or struggles of national liberation (such a designation is often subject to controversy):

Many Chechens and foreign observers consider the First and Second Chechen Wars to be wars of national liberation against Russia.
Some Iraqi insurgent groups, and certain political groups believe that the Iraq War was a war of national liberation against the US-led coalition.
Many Kurds believe the Kurdish–Turkish conflict to be a war of national liberation of Kurdish people in Turkey.
The Polisario Front has sought the independence of Western Sahara since 1975 and considered its guerrilla war against Morocco as national liberation war (like many foreign observers, countries and the African Union), while Morocco considered it a secessionist movement. Polisario had been recognized by many countries, the African Union and the United Nations as the legitimate representative of the Sahrawi people. The hostilities are frozen since the 1991 cease-fire following the settlement plan agreement.

Conflicts: Conflicts which have been described as national liberation struggles:

The Swedish War of Liberation (1521–23).
The Eighty Years' War.
The Khmelnytsky Uprising.
The American Revolutionary War.
The Irish Rebellion of 1798.
The Irish Rebellion of 1803.
The Peninsular War against Napoleon's occupation of Spain and Portugal during the Napoleonic Wars.
The Haitian Revolution.
The German campaign of 1813 against Napoleon's occupation of German lands during the Napoleonic Wars.
The Spanish American wars of independence.
The Swedish-Norwegian War.
The Greek War of Independence (1821).
The Serbian Revolution.
The Dominican War of Independence (1844–1856).
The Italian Wars of Independence (1848-1866)
The Dominican Restoration War (1863–1865).
The Serbian–Turkish Wars (1876–1878).
The  Portuguese Restoration War
Explicit wars of decolonization:
The Philippine Revolution
The August Revolution, Việt Minh against Japanese invasion of Vietnam.
The First Indochina War, Viet Minh against French colonial rule in Indochina
The Indonesian National Revolution
The Tamil resistance to Sri Lankan colonization in Tamil-speaking territories and discrimination against the Tamil people.
The Malagasy Uprising against French colonial rule in 1947.
The Algerian War against France (1954–1962).
The Portuguese Overseas War in Angola, Guinea-Bissau, and Mozambique against Portugal (1961-1974).
In Cameroon, by the UPC against France.
In South Yemen by the National Liberation Front (NLF) and the Front for the Liberation of Occupied South Yemen (FLOSY).
The Mau Mau Rebellion against British rule in Kenya.
The Rhodesian Bush War in white-ruled Rhodesia (now Zimbabwe), led by ZANU and ZAPU.
In Western Sahara, by the Moroccan Army of Liberation against Spain & France, and by the Polisario Front against Moroccan & Mauritanian occupation.
In Namibia, by the South West Africa People's Organization (SWAPO) and SWANU against apartheid South Africa.
The Dhofar Rebellion in Muscat and Oman.
The Dervish War in Somalia.
The Brunei Revolt.
The Estonian War of Independence.
The Latvian War of Independence.
The Lithuanian Wars of Independence.
The Ukrainian War of Independence.
The Turkish War of Independence.
The National Liberation War and Socialist Revolution of Yugoslavia within World War II, by the Yugoslav Partisans (National Liberation Army) against Axis occupators and their collaborators.
The Italian Civil War in which forces of the Kingdom of Italy and the Italian resistance movement fought against occupying forces of Nazi Germany and forces of the Italian Social Republic during the Italian campaign of World War II.
In China, the Chinese Civil War (1945–1949).
In North Korea, the Korean War against South Korea.
The Vietnam War, with South Vietnam and the United States against North Vietnam, China, Soviet Union and communist bloc.
The Eritrean War of Independence against Ethiopia.
The Bangladesh Liberation War against West Pakistan.