After Korea (1950), the next crisis was Suez, but that one (for better or worse) set the tone for later UN missions:
According to the UN usage, the term "peacekeeping" originated
with the UN Emergency Force (UNEF) stationed in the Middle East
to vacate the tripartite aggression of Israel, France and Britain in Egypt
in 1956. The succeeding UN undertakings during the 1970s and 80s,
that were similar but not exact to the UNEF, were also referred to as
UN peacekeeping. Among these were the UN involvements in Leba
non (UNOGIL) in 1958, in the Congo (ONUC) in 1960, in Yemen
(UNYOM) in 1963 and 22 others afterwards. However, the recent UN
involvements in Cambodia, Somalia and Bosnia Hercegovina seem to
reflect drastic departures from the original principles of peacekeeping
that were enunciated or crystallized in the creation and the
operationalization of the UNEF in 1956.
The UNEF was deliberately designed to be completely different
from the first major military enforcement by the UN, under Chapter
VII of the UN Charter, taken in 1950 to meet the challenge of
aggression by communist North Korea and China on the pro-West
South Korea. But the aggressors in the Suez crisis were Western allies,
not communist antagonists of the Western bloc. Therefore, the Western powers had to design different goals and operations for the UNEF
even though aggression was the common feature in both Korea and the
Suez.
[...]
Many non-Westem countries and the Communist states wanted
the UN to take against the three Suez aggressors the exact actions that
were taken against North Korea and China in 1950 — a clear identification and condemnation of the aggressors, followed by the UN
military enforcement under Chapter VII all within days and weeks. Of
course, the Cold War practitioners could not have been so impartial
and objective. The US had not named Britain, France or Israel the
aggressors, as it had named North Korea and China in the Korean
crisis. Nor did the US invoke Chapter VII of the Charter dealing with
military enforcement.
After many ups and downs, the UN agreed to create a UN force
that could be inducted into Egypt to provide a cover for the three
aggressors to withdraw. But the UN force was to act like a police force rather than a fighting force. This UN operation came to be known as
UN peacekeeping as the UN force for peacekeeping in the Suez was
christened UN Emergency Force (UNEF). This development established the principle that UN peacekeeping need not start with the
determination of the guilt of any party, as is necessary under peace
enforcement.
[...]
The operationalization of the UNEF produced the following rules
of peacekeeping. Firstly, military hostilities should cease before any
peacekeeping can be undertaken by the UN. Secondly, the determina
tion under Article 39, of an "act of aggression" or a "breach of the
peace," or even "a threat to the peace" is not necessary to initiate a
peacekeeping measure. Thirdly, as indicated in the Secretary General
Hammarskjold's "Second and Final Report" of 1956, the UNEF was
not meant to be a fighting force as was the UN-US force in Korea
(1950). The special role assigned to the UNEF was policing the cease
fire terms and the truce lines, and patrolling the borders against
infiltration of armies, weapons or trouble-makers. Though UN peace
keeping, as such, is not envisaged in the Charter, the UNEF activities
could be derived from various provisions of the Charter. Most constitutionalists locate the powers of UN peacekeeping in Chapter VI.
Three important consequences flow from such constitutionalization
of UN peacekeeping: (1) Because UN peacekeeping is not UN
enforcement, the UNEF could not engage in any military combat
except in the extreme situations of the need for self-protection. (2) Not
being an enforcement action, peacekeeping role cannot disregard or
corrode national sovereignty. A corollarly of sovereignty is the UN
guarantee of non-intervention in domestic jurisdiction [Article 2(7)].
(3) Not being a fighting force, the UNEF should not be equipped with
heavy combat weaponry; only light armour suitable for self-defense
under extreme danger, is permitted.
And after that came Congo (1960) where things eventually turned a little different:
Katanga and South Kasai seceded with Belgian support. Amid continuing unrest and violence, the United Nations deployed peacekeepers, but UN Secretary-General Dag Hammarskjöld refused to use these troops to help the central government in Léopoldville fight the secessionists. Prime Minister Patrice Lumumba, the charismatic leader of the largest nationalist faction, reacted by calling for assistance from the Soviet Union, which promptly sent military advisers and other support.
[...] the UN took a more aggressive stance towards the secessionists after Hammarskjöld was killed in a plane crash in late 1961. Supported by UN troops, Léopoldville defeated secessionist movements in Katanga and South Kasai by the start of 1963. [...]
In December 1961, UN troops from Sweden, Ireland, India, and Ethiopia were involved in heavy fighting for Katanga's capital, Elizabethville. UN forces eventually managed to defeat the Katangan gendarmes in the city and took Elizabethville. During the fighting, eleven Swedish soldiers were taken prisoner; they were released on 15 January 1962 in exchange for Katangan gendarmes.
In August 1961, under the command of Indian Army's Brigadier-General K.A.S. Raja, the UN launched Operation Rumpunch, a surprise attack that led to the peaceful surrender of 81 foreign mercenaries.
On 13 September 1961, the most obvious example of the transition from peacekeeping to peace enforcement occurred when the Indian ONUC leadership on the ground leading an Indian brigade, launched "Operation Morthor" (Hindi: twist and break) and swiftly took control of Katanga. The operation was meant to be a stepped up version of the earlier Operation Rumpunch. However, Hammarskjöld was not fully informed and did not know the operation was happening.
So, yeah, the UN helped defend Congo from (what were at least initially) Belgium-sponsored secessionists. But it also involved Indian troops partially acting outside the direct orders of the UN! And things didn't stop there... After some ceasefires etc.
The situation came to a breaking point on 24 December 1962 when Katangan gendarmes brazenly attacked peacekeeping forces in Katanga, causing [the new UNSG] Thant to authorize a retaliatory offensive to decisively eliminate secessionist opposition.
Major General Dewan Prem Chand launched Operation Grandslam on 28 December and by the end of the day UN troops had seized downtown Élisabethville [again!]
And
Indian peacekeepers [again] surpassed their orders and crossed the Lufira River ahead of schedule, generating panic behind the Katangan lines and causing an incident among United Nations leadership.
But, it should not be underestimated how unpopular the UN was then ... in Belgium and even other parts of Europe!
Anti-U.N. articles appeared in newspapers in Belgium and, indeed,
elsewhere in Europe. In Britain, for example, the U.N. force in the
Congo was called 'The Red Army in blue berets'. [...]
There were rumours that Hammarskjold
represented a large group of Swedish or (according to some variant
both Swedish and American mining companies in the Congo, and that
they were attempting to put the Belgians out of business. Such reports
hinted that the U.N. Secretary-General, one of the world's most
esteemed personalities, was motivated by considerations of financial
gain. These allegations circulated widely, especially in Belgium, having
started from the very beginning of the crisis and continuing after
Hammarskjold's plane had crash.
In December 1961, La Libre Belgique (Brussels), a conservative daily
noted reports of 'a Swedish-American concern... set up for the purpose
of gaining control over the nonferrous metals in the Congo. A relative
of Mr. Hammarskjold was the kingpin of this trust'. [...] and the U.N. action was termed 'a case of sinister international capitalism' by a Tory M.P. in Britain.
However the opinion was not widely held outside Belgium then... although as that paper analyses, the connections between the Hammarskjold family and some Swedish mining interests (Lamco) that were assisting the UN Congo on the economic side did in fact exist, via Hammarskjold's brother Bo, who was on the board of directors of one of Lamco companies. The paper (by a US academic) however concludes
The obvious question at this point is the following: So what? There
is no hard evidence that Swedish business interests actually influenced
U.N. policy in the Congo.
Likewise though, there were US business shares in the Swedish companies too and
America was encouraging Hammarskjold's anti-Katanga
policies - the Kennedy Administration strongly opposed the secession,
the bulwark of the Belgian interests - and was providing much of the
finances for the U.N.'s Congo operation.
So, you can see why peacekeeping turned anti-secessionist peace enforcement was somewhat controversial politically for those reasons too.
There's quite a bit more to say about Thant, but this will probably suffice:
Later Thant would write, somewhat proudly, that ONUC proved to be the "first experience, under combat conditions in the field, of an armed force composed strictly of international units and strictly under UN command." The UN force was robust, even by today's standards. It acquired artillery, tanks and fighter jets. It dropped bombs (including inadvertently on a hospital, something not often mentioned). It developed a sophisticated intelligence-gathering system and it did take offensive action, despite claims that it was acting in self-defence only.
Thant may have had deeper reasons for his aversion to Katangan secession and civil war. For one, his native land Burma (and Thant himself) had suffered enormously from secessionist attempts (the Karen insurgency) shortly after independence. He had also seen at close hand the devastating effects of the 1947 partition of India. As secretary-general during a period of widespread decolonization, Thant was also keenly aware of the precarious state of many Afro-Asian territories. Should secession be recognized or encouraged in one country, it could easily spread to others. Thant, the United Nations and almost all members of the international community strongly supported the territorial integrity of former colonies and emerging states. Thant expressed anti-secessionist sentiments strongly in February 1970: the United Nations "has never accepted and does not accept, and I do not believe it will ever accept, the principle of secession of a part of its Member State." The UN's acceptance of some twenty secessions in the former Communist bloc the 1990s was to prove his prediction wrong, though the principle of territorial integrity remains strong in the international community.
However, in the long run, Congo has still been quite unstable. Ironically perhaps, a day or so ago, Congo asked the 20-years old MONUSCO mission to GTFO basically as it's been unable to keep the peace in the midst of several factions... including:
Eastern Congo has long been overrun by dozens of armed groups seeking a share of the region’s gold and other resources. Some have been quietly backed by Congo’s neighbors. U.N. experts have noted “substantial evidence” that Rwanda is supporting the resurgent M23 rebel group, which Rwanda has denied.
Generally speaking though, the conclusion from much of that was to go along closer to the lines of UNEF rather ONUC. For instance, the semi-famous Brahimi report of 2000, when a panel was convened for the purpose of reviewing the logic of UN peacekeeping in general, concluded that:
The Panel concurs that consent of the local parties, impartiality and the use of force only in self-defence should remain the bedrock principles of peacekeeping.
OTOH, no doubt with reference to Bosnia, Rwanda etc., they added:
No failure did more to damage the standing and credibility of United Nations
peacekeeping in the 1990s than its reluctance to distinguish victim from aggressor. [...]
United Nations peacekeepers — troops or police — who witness
violence against civilians should be presumed to be authorized to stop it, within
their means, in support of basic United Nations principles. However, operations
given a broad and explicit mandate for civilian protection must be given the specific
resources needed to carry out that mandate.
However, going from theory to practice can be pretty hard on striking that balance, as we saw plenty of failures for the UN recently--besides Congo also MINUSMA was kicked out of Mali etc.
So, given such scaled-back mandates/expectations, the UN kicking out the (ironically/misleadingly named) "Unity for Peace in Central Africa" (UPC) out of Boyo (in 2021), probably counts as a success of sorts:
The UN Multidimensional Integrated Stabilization Mission in the CAR, known by its French acronym MINUSCA, launched an operation on Saturday to expel from Boyo, in Ouaka prefecture, around 200 members of the armed group Unity for Peace in Central Africa (UPC).
According to MINUSCA, Nepalese and Mauritanian battalions arrived to support ground efforts, forcing the UPC combatants to vacate the town.
They had taken over numerous homes, including the mayor's residence.
The Mission drew attention to more than a dozen civilian fatalities on 6 and 7 December in Boyo, which also prompted the displacement of nearly 1,500 people.
The UN peacekeepers were able to intervene to protect civilians and continue their operations throughout the city with robust patrols.
MINUSCA sent out a warning to the UPC against any attempt to re-occupy Boyo and reaffirmed its determination to ensure the protection of communities in accordance with its mandate.
And since one might have trouble finding Boyo on a map....
Essentially, the UN peacekeepers can prevent small-scale warlordism.
BTW, two of those recently failed UN missions (Congo and Mali) were in fact given extended powers, beyond traditional peacekeeping, so a wee bit harking back to Congo '60; as this 2015 piece details
On June 16 [2015], the UN secretary General’s High-Level Independent Panel released its eagerly awaited review of UN-mandated peacekeeping: ‘Uniting our Strengths for Peace’. [...]
a striking feature of recent UN operations has been the Security Council’s practice of enshrining the classic principles of peacekeeping into mission mandates. Starting with the 2013 renewal of MONUSCO’s mandate, the Security Council has consistently re-affirmed the ‘trinity of virtues’ – impartiality, host state consent and non-use of force beyond self-defence and defence of the mission mandate – in the preambles of its largest peacekeeping operations (DRC: 2013, 2014, 2015; Mali: 2013, 2014, 2015; CAR: 2014, 2015; South Sudan: 2014, 2015). Although their status under international law remains contested, the three classic principles are grounded in an (almost) by-gone era of conflict-management, where UN peacekeepers monitored mutually agreed cease-fires.
While such peacekeeping missions still exist (e.g. Cyprus), this no longer reflects the realities of modern conflict. In the DRC, where over thirty armed groups operate in the vicinity of UN peacekeepers, the Security Council decided in 2013 to create an Intervention Brigade to:
“carry out targeted offensive operations… in a robust, highly mobile and versatile manner… to prevent the expansion of all armed groups, neutralize these groups, and to disarm them…” (SC Res 2098; para. 12 (b)).
In Mali, where the UN is bogged down in operations against terrorist groups that have cost the lives of dozens of peacekeepers, MINUSMA is authorised:
“to stabilize the key population centres, notably in the North of Mali, and… to deter threats and take active steps to prevent the return of armed elements to those areas” (SC Res 2100, para. 16 (a) (i)).
In light of such pro-active authorisations to use military force, one could easily conclude that the Security Council’s invocation of classical peacekeeping principles is little more than window-dressing. But it creates very real legal dilemmas in the field, most notably with respect to maintaining the protected status of UN personnel, the detention and internment powers of UN operations, responsibility for human rights law violations, translating principles on the use of force into operational guidelines, and criminal accountability for killing peacekeepers.
[...] Urging a ‘flexible and progressive’ understanding of the core peacekeeping principles, the report suggests there is no insurmountable incompatibility between using force to eliminate some parties to a conflict and a mission’s impartiality or the principle of consent. With respect to peace enforcement, including neutralising and defeating a ‘designated enemy’, the Panel says only that such military operations should be ‘exceptional’ and ‘time-limited’. Regarding terrorism, it recommends, in surprisingly categorical language, that the UN should not be involved in any counter-terrorism operations going forward.
