By 1973, the war had become increasingly unpopular due to its length and financial costs, the worsening of diplomatic relations with other United Nations members, and the role it had always played as a factor of perpetuation of the entrenched Estado Novo regime and the nondemocratic status quo in Portugal.

[45] However, the Portuguese traders and explorers settled in the coastal strip with greater success, and established strongholds safe from their main rivals in East Africa – the Omani Arabs, including those of Zanzibar.

[50] NATO's focus on preventing a conventional Soviet attack against Western Europe was to the detriment of military preparations against guerrilla uprisings in Portugal's overseas provinces that were considered essential for the survival of the nation.

Some analysts see the "Botelho Moniz coup" of 1961 (also known as A Abrilada) against the Portuguese government and backed by the U.S. administration,[51] as the beginning of this rupture, the origin of a lapse on the part of the regime to keep up a unique command center, an armed force prepared for threats of conflict in the colonies.

Instead, after a coup led by pro-U.S. forces failed to depose him,[citation needed][specify] Salazar consolidated power and immediately sent reinforcements to the overseas territories, setting the stage for continued conflict in Angola.

[83] Angola enjoyed an unprecedented economic boom during the 1960s, and the Portuguese government built new transportation networks to link the well-developed and highly urbanized coastal strip with the remote inland regions of the territory.

Much of the initial offensive operations against Angolan UPA and MPLA insurgents was undertaken by four companies of Caçadores Especiais (Special Hunter) troops skilled in light infantry and antiguerrilla tactics, and who were already stationed in Angola at the outbreak of fighting.

Distances from the major Angolan urban centres to neighbouring Zaïre and Zambia were so large that the eastern part of Angola's territory was known by the Portuguese as Terras do Fim do Mundo (the lands of the far side of the world).

Defensive operations, where soldiers were dispersed in small numbers to guard critical buildings, farms, or infrastructure were particularly devastating to the regular Portuguese infantry, who became vulnerable to guerrilla attacks outside of populated areas by the forces of the PAIGC.

General Spínola's Africanization policy also fostered a large increase in indigenous recruitment into the armed forces, culminating the establishment of all-black military formations such as the Black Militias (Milícias negras) commanded by Major Carlos Fabião.

Naval amphibious operations were instituted to overcome some of the mobility problems inherent in the underdeveloped and marshy areas of the territory, using Destacamentos de Fuzileiros Especiais (DFE) (special marine assault detachments) as strike forces.

One immediate result of Operation Green Sea was an escalation in the conflict, with countries such as Algeria and Nigeria now offering support to the PAIGC as well as the Soviet Union, which sent warships to the region (known by NATO as the West Africa Patrol) in a show of force calculated to deter future Portuguese amphibious attacks on the territory of the Guinea-Conakry.

The OAU established a committee based in Dar es Salaam, with representatives from Ethiopia, Algeria, Uganda, Egypt, Tanzania, Zaire, Guinea, Senegal, Nigeria, to support African liberation movements.

Based on their analysis of operations in those theatres and considering their own situation in Africa, the Portuguese military took the unusual decision to restructure its entire armed forces, from top to bottom, for counterinsurgency.

[107] At the beginning of the war, the elite airborne units (Caçadores Pára-quedistas) rarely used the m/961, having adopted the modern 7.62 mm NATO ArmaLite AR-10 (produced by the Netherlands-based arms manufacturer Artillerie Inrichtingen) in 1960.

[112] The powerful recoil and heavy weight of the 7.62mm NATO cartridge used in Portuguese rifle-caliber arms such as the m/961 limited the amount of ammunition that could be carried as well as accuracy in automatic fire, generally precluding the use of the latter except in emergencies.

While the heavy m/961 and its relatively lengthy barrel were well-suited to patrol operations in open savannah, it tended to put Portuguese infantry at a disadvantage when clearing the low-ceilinged interiors of native buildings or huts, or when moving through thick bush, where ambush by a concealed insurgent with an automatic weapon was always a possibility.

Apart from these limited exceptions, Portugal was faced with UN-sponsored sanctions, Non-Aligned Movement-led defamation, and myriad boycotts and protests performed by both foreign and domestic political organizations, like the clandestine Portuguese Communist Party (PCP).

The guerrillas' AKM rifles and such variants were highly thought of by many Portuguese soldiers, as they were more mobile than the m/961 (G3), while permitting the user to deliver a heavy volume of automatic fire at the closer ranges typically encountered in bush warfare.

Mines and other booby traps were one of the principal weapons used by the insurgents against Portuguese mechanized forces to great effect, who typically patrolled the mostly unpaved roads of their territories using motor vehicles and armored scout cars.

After the electoral fraud of 1958, Humberto Delgado formed the Independent National Movement (Movimento Nacional Independente – MNI) that, in October 1960, agreed that there was a need to prepare the people in the colonies, before giving them the right of self-determination.

[123][124] Faced with government inflexibility over proposed reforms, some Portuguese junior military officers, many from underprivileged backgrounds and increasingly attracted to the Marxist philosophy of their African insurgent opponents,[76] began to move the MFA to the political left.

General Spínola was invited to assume the office of President, but resigned a few months later after it became clear that his desire to set up a system of federalized home rule for the African territories was not shared by the rest of the MFA, who wanted an immediate end to the war (achievable only by granting independence to the provinces of Portuguese Africa).

After the coup on 25 April 1974, while the power struggle for control of Portugal's government was occurring in Lisbon, many Portuguese Army units serving in Africa simply ceased field operations, in some cases ignoring orders to continue fighting and withdrawing into barracks, in others negotiating local ceasefire agreements with insurgents.

[125] According to Guilherme Alpoim Calvão, for a brief time after the 25 April Coup (May 1974 – November 1975), Portugal was on the brink of Civil war between left-wing hardliners (Vasco Gonçalves, Otelo Saraiva de Carvalho and others) and the moderate forces (Francisco da Costa Gomes, António Ramalho Eanes and others).

The departure of the Portuguese from Angola and Mozambique increased the isolation of Rhodesia, where white minority rule ended in 1980 when the territory gained international recognition as the Republic of Zimbabwe with Robert Mugabe as the head of government.

Nevertheless, most accepted the inevitable, and while an abortive right-wing settler revolt broke out in Mozambique, it quickly died out as Portuguese coup leaders made it clear that the decision to grant independence was irrevocable.

[22] In a statement in the party newspaper Nô Pintcha (In the Vanguard), a spokesman for the PAIGC revealed that many of the ex-Portuguese indigenous African soldiers that were executed after cessation of hostilities were buried in unmarked collective graves in the woods of Cumerá, Portogole, and Mansabá.

In 2007, a Radiotelevisao Portuguesa (RTP) documentary by Joaquim Furtado, made public both these government-supported atrocities and the organized massacres and terror campaign policies of some pro-independence guerrilla movements or their supporters; it was watched by over a million people, a tenth of the population at the time.

[138] On 13 November 1972, a sovereign wealth fund was enacted through the Decree Law Decreto-Lei n.º 448/ /72 and the Ministry of Defense ordinance Portaria 696/72, in order to finance the counterinsurgency effort in the Portuguese overseas territories.