A relief column of approximately 500 Indian, Irish, and Swedish UN troops, sent to break the siege, was unsuccessful and suffered several casualties (including at least five killed).

[17] The Congo's economy was dominated by Belgian and British business firms, the most powerful of which were the Belgian-owned Société Générale de Belgique and the British-owned Union Minière du Haut Katanga.

[18] Following the Congolese declaration of independence in June 1960, in pursuit of retaining economic benefits, the Belgian government supported the secession of the Katanga Province under Moise Tshombe, which began the Congo Crisis.

[21] The already politically complex position of Belgium was further complicated by Prime Minister Tshombe's appointment to America of a Belgian civil servant, Michel Struelens, to promote the international reputation of Katanga and its independence through propaganda.

[19] Following the torture and killing of Lumumba on 17 January 1961 under orders from Tshombe and with indirect assistance of the Belgian state, the UN Security Council passed Resolution 161A a month later on 21 February 1961.

[26] Prior to being deployed to Katanga in June 1961 as part of the ONUC mission, Conor Cruise O’Brien was an Irish diplomat within the UN foreign office in the Republic of Ireland.

[30] Prior to its start, on 24 August, both President Kasavubu and newly appointed Prime Minister Cyrille Adoula issued orders for the removal of "all non-Congolese officers and mercenaries", and for UN assistance in this action.

[33] As a result of Operation Rumpunch, Katangan Minister Godefroid Munongo ramped up actions against those who were anti-secession, which led to 45,000 people seeking assistance from the UN compound in Elisabethville.

According to both Conor O’Brien and General McKeown this decision was made due to the petition of Belgian Foreign Minister Paul Spaak to protect the white population at Jadotville.

[34] The launching of Operation Morthor is considered controversial due to the contention that it was outside the remit given to ONUC,[35] even by the February Security Council Resolution.

This mission had a similar purpose to Operation Rumpunch, with UN troops attempting to take control of the means of communication (radio station and post office), alongside arresting the remaining mercenaries.

British Prime Minister Harold Wilson compared the UN peacekeepers’ actions to those of the Soviet Union, by calling them "The Red Army in blue berets".

[41] On 5 September the Katangan forces began constructing roadblocks on the roads available to Company A, which prompted Commandant Quinlan to order his men to build further trench fortifications.

The Irish soldiers were armed with personal weapons, several water-cooled Vickers machine guns, 60mm mortars and two Irish-built Ford Mark VI armoured cars under the command of Lieutenant Kevin Knightly (the Fords were armed with one Vickers machine gun each, mounted in their cupolas – reportedly firing 15,000 rounds of ammunition over the next four days).

[51] The supporting force of mercenaries (many of them French, German, Belgian and South African; almost all veterans of the Algerian War) beat back these efforts.

[57] On 14 September, the Katangan Fouga jet flew passes over the battlefield, dropping bombs that rendered the Company's vehicles inert[58] and caused injuries to two Irish soldiers.

Later that same day, a ceasefire agreement was reached between Quinlan and the Burgomaster of the Katangan forces, enabling the Irish troops to re-supply with water; the Gendarmerie retreated from their positions surrounding the UN compound.

[61] Quinlan lacked any clear direction or communication from his superiors, and the Katangese gradually infringed on the ceasefire agreement to undermine "A" Company's position.

With his position untenable --without any clear orders or promise of assistance, having run out of ammunition and food and being low on water-- Quinlan accepted their second offer to surrender.

[43][45] On 17 September, Quinlan met with Katanga Minister Munongo, in which a formal written ceasefire and surrender agreement was made, which contained the proviso that the Irish Company would keep their weapons and be unharmed.

[10] While Operation Morthor was halted by Secretary General Hammarskjöld, its failure and the bloodshed it caused led to an anti-UN campaign by Katanga.

[38] In January 1963, UNOC'S Operation Grandslam decisively defeated the forces of the self proclaimed State of Katanga, reintegrating the region into the Congo, while Moïse Tshombe fled the country.

[38] The various failures of the UNOC mission during 1961, including the assassination of Prime Minister Patrice Lumumba and the death toll of Operation Morthor, led elements of the UN to downplay attention to the Siege of Jadotville.