[4][5] During this period, the lands constituting what would eventually become the Congo Free State were placed under the sole, private ownership of King Leopold II of Belgium at the Berlin Conference in 1885.

[12][13]: 246 [14]: 612–613 In the 1930s, the Belgian colonial administration established a system of encouraging immigration from Ruanda-Urundi to the eastern Congo, both to mitigate population density in the former and provide agricultural labour to the latter.

[18] Both colonies were impacted by World War II; the role of the Congo, and especially it's abundance of raw materials,[19][20] became of interest to the Allies after a German invasion forced the Belgian government into exile in 1940.

[29][30] During this period, Tutsi insurgent groups began launching largely unsuccessful attacks against the Hutu-dominated Rwanda, including the December 1963 Bugesera invasion.

[36] Frustrated that Congolese authorities hampered their activities, and radicalised by their repeated failures, Tutsi Rwandan rebels based in the Congo joined the Lumumbist Simba rebellion, because they hoped that a Simba-led government would support their own efforts in Rwanda.

Even though the vast majority of Rwandans in the Congo were uninvolved in the uprising and living peacefully, they were consequently the target of ethnic violence and blamed "for all sorts of evil" by Congolese authorities.

[41] The "Rwanadese Popular Movement" and the "Rwanda Youth National Union" led by Jean Kayitare, son of Rwandan exile leader François Rukeba, each mobilized a battalion to assist the beleaguered Simbas.

[39] One Rwandan rebel leader told Che Guevara that he was losing so many of his fighters that the exiles' plans to invade Rwanda in future had become almost impossible.

[47][48] These moves aggravated existing ethnic tensions, as it strengthened the Banyarwanda's hold over important stretches of land in North Kivu that indigenous people claimed as their own.

[46] From 1963 to 1966 the Hunde and Nande ethnic groups of North Kivu fought against Rwandan emigrants[49] — both Tutsi and Hutu – in the Kanyarwanda War, which led to several massacres.

[53] President Mobutu attempted to provide support to Rwanda by sending hundreds of troops from the elite Special Presidential Division (DSP).

[76][77] Given the exacerbated ethnic tensions, the lack of government control in the past, and Mobutu's support for the Hutu rebels,[75][78] Rwanda took action against the security threat posed by génocidaires in eastern Zaire.

[80] Banyamulenge elements and non-Tutsi militias coalesced into the Alliance des Forces Démocratiques pour la Libération du Congo-Zaïre (AFDL) under the leadership of Laurent-Désiré Kabila, a long-time opponent of the Mobutu government and former participant of the Simba rebellion.

Kagame claimed that Rwandan agents had discovered the plans to invade Rwanda with support from Mobutu; in response, Kigali began its intervention with the intention of dismantling the refugee camps in which the génocidaires often took refuge and destroying the structure of these anti-Rwandan elements.

[82] With the active backing from Rwanda, Uganda and others, the AFDL began to occupy large portions of Zairian territory between October 1996 and May 1997, encountering very little resistance.

When Kabila gained control of the capital in May 1997, he faced substantial obstacles to governing the country, which he renamed the Democratic Republic of the Congo (DRC).

[94] Congolese in the capital resented this, who began to see Kabila as a pawn of foreign powers,[a] as did many in the eastern Kivu provinces, where ethnic clashes increased sharply.

[96] Tensions reached new heights on 14 July 1998, when Kabila dismissed his Rwandan chief of staff James Kabarebe, and replaced him with a native Congolese, Célestin Kifwa.

[100]The Second Congo War initially began 2 August 1998 with a Banyamulenge rebellion in Goma,[101] followed by Rwanda backing rebels from the Rally for Congolese Democracy (RCD).

[109][110] In April 2001, a United Nations panel of experts investigated the illegal exploitation of diamonds, cobalt, coltan, gold and other lucrative resources in the Congo.

The report accused Rwanda, alongside Uganda and Zimbabwe, of systematically exploiting Congolese resources and recommended the Security Council impose sanctions.

[112] His son, Joseph, was appointed president and immediately began asserting his authority by dismissing his father's cabinet and senior army commanders,[113] assembling a new government, and engaging with the international community.

[116] Kagame blamed the DRC for failing to suppress the Democratic Forces for the Liberation of Rwanda (FDLR), a rebel group led by Rwandan Hutu operating in North and South Kivu.

[125] Although they were defeated in 2013, M23 fighters who fled to Rwanda and Uganda started crossing back into the DRC during a rising crisis over Kabila extending his term limit.

[126][127] After Félix Tshisekedi was sworn into office as Kabila's successor in January 2019,[128][129] he initially had a friendly relationship with Kagame, with the countries appearing to move towards normalizing relations.