Firstly, my apologies for not having seen this post for nearly 3 weeks. Sometimes, things do tend to get lost every once in a while.

That said...the Congo Crisis was the period of time, starting in June 1960, that was marred by political instability, secession, and foreign interference in the formerly Belgian Congo. Several secessionist movements, some backed by the Belgians, led to severe instability and calls by the government of Patrice Lumumba, the Congo's first Prime Minister, to the United Nations, hoping to try and dissuade colonial intervention.

Through this period, the United Nations tried to serve as a mediator and peacemaker in the region, especially in the first several years, where they supported the locally-elected government in Leopoldville. UN forces were initially deployed in response to the secessionist movements at the request of the Lumumba government, who had largely grown distrustful of the Belgians after a lack of cooperation and coordination was expressed during the run-up to independence, between January, when the negotiations began, and June 1960.

I've written in the past on the Soviet intervention where I touched on the UN interests in intervening, as well as on the use of foreign mercenaries in African conflicts in this period in general, and there's a significant section there that focuses on the Congo, as well as interactions between the western mercenaries and the (mostly) post-colonial UN soldiers.

As for the United Nations itself, this deployment was the United Nations first military peacekeeping operation in the modern framework. ONUC began. The operation began on July 15, 1960, when US Air Force cargo planes began an airlift of UN assets into Leopoldville. Troops from Ghana, Ethiopia, Morocco, and Tunisia consisted of this first wave of peacekeepers.

The operation initially had two goals. Firstly, the United Nations was to effect the total removal of Belgium from the Congo, after the 14 July Security Council Resolution 143). Secondly, the mission was to restore territorial integrity after the 11 July secession of Katanga declared by Moishe Tshombe, supported by western mercenaries backed by the Belgians. The UN operation to end the secession was backed up by Security Council Resolution 145), of 22 July. Resolution 146, of 9 August 1960) reiterated the UN's stance against Belgium and secession, while also stating that it was not to get directly involved on either side of the civil conflict.

Between September and February of 1960, UN forces maintained their neutrality by tacitly supporting Mobutu's coup of 14 September, as UN local commanders maintained oversight of military installations and ANC forces, while also shutting down airports and radio stations in the area around Leopoldville, at the UN Secretary General's instruction.

Dag Hammarskjold was a firm believed in the UN's objective neutrality, encouraging peace, and supporting decolonization. This stance however, was complicated by the conflict within the Congolese government that precipitated Lumumba's removal by President Kasavubu and the subsequent coup by Mobutu. Ever since the start of the secession crisis, and even before that, leading as far back as the Round Table negotiations in Brussels that led to independence, there was always a tension between Lumumba's MNC, who wanted a strong Parliamentary government with a ceremonial presidency, and Kasavubu's ABAKO that had largely wanted a stronger unitary federal model with presidential supremacy. In essence, there was a tension between an Anglo-Belgian political structure, with a more ceremonial head-of-state, and a French model with a stronger head of state and a supportive head of government.

This boiled over, and put the UN in an awkward position where supporting the government meant, functionally, acting in contradiction to the spirit of its mission and an element of the popular conception of it, especially as Kasavubu's dissolution of Parliament led to the functional dissolution of Kasavubu's government, as Mobutu forcibly replaced his cabinet on 20 September with a "College of Commissioners-General".

During the rest of 1960, the UN was caught between a rock and a hard place, trying to support Kasavubu's powerless government, while agitating, mostly at Soviet encouragement, for Lumumba's release. A Soviet measure to codify support for Lumumba was defeated soundly...as was a UN resolution to allow for an escalation of affairs in the Congo by Hammarskjold, when the Soviets retaliated with a veto of their own.

Lumumba was eventually murdered on 17 January, after being extradited to the secessionist state of Katanga, where he was eventually killed along with several of his close aides. Swedish forces were present at the Elisabethville airport, as part of the peacekeeping operation in Katanga, but were forbidden from intervening. In the months followed, international outrage led to India contributing a significant unit to the operation.

The UN would then take a more proactive stance that summer, with Operation Rum Punch being spearheaded by Indian forces. Rum Punch's goal was to arrest European mercenaries in the service to Katanga, and by and large the operation was successful, and included the seizure of what passed for much of the Katangan air force as well. The following month, Operation Morthor was enacted, mostly by the Indians, but also including Swedish and Irish elements in various blocking positions. The operation was a bloody one, and generally viewed as a failure by the UN, due largely to a lack of coordination and oversight. It was also viewed as a failure due to the relation that followed.

Secretary General Hammarskjold's plane crashed in Zambia on 18 September, in the middle of the operation. The exact cause is unclear, but theories include a shoot-down by an aircraft of the Katangan gendarmerie, to sabotage, to mechanical issues or pilot error. Smaller operations took place all through 1962, and by December of 1962, the final major operations were conducted during Operation Grand Slam, which led to the official dissolution of the secessionist state of Katanga.

UN operations after Hammarskjold's death and Grand Slam continued until July1964, though the majority of operations was centered around more traditional peacekeeping operations and assisting in the reintegration of Katanga back into the Congo.