On the one side is Tanzania, exasperated by a flood of refugees fleeing fighting in the Democratic Republic of Congo’s eastern Kivu region — the scene of years of back-to-back wars involving regional powers.
Tanzania has joined a new United Nations brigade fighting alongside the Congolese army against the myriad rebel and militia forces that keep the region in anarchy.
The intervention force, given an unprecedented offensive mandate by the UN Security Council, is being heralded as a bid to bring an end to the Kivu conflict once and for all.
But this has put Tanzania on a collision course with Rwanda, seen as a key backer of one of the main rebel groups in North Kivu, and opposed to negotiations with another militia made up of Hutu extremists it accuses of responsibility in the Rwandan genocide nearly 20 years ago.
“The Tanzanians are fed up” with the chronic instability in the Great Lakes region, explained Andre Guichaoua, a professor at France’s Sorbonne University.
Guichaoua said Tanzanian President Jakaya Kikwete is convinced his Rwandan counterpart Paul Kagame is “stoking up the conflict”.
Despite official denials, Rwanda is widely seen as the primary backer of the M23 rebels, a Congolese faction that has emerged as one of the most formidable forces operating in the east and threatening Goma, the capital of North Kivu province.
The outcome has been a war of words between the two leaders and something approaching a proxy war on the ground.
Tensions worsened at an African Union meeting in May, when the Tanzanian leader urged Kagame — as well as Congo’s Joseph Kabila and Uganda’s Yoweri Museveni– to hold talks with the rebels fighting them.
For Kagame, a savvy former guerrilla commander who took power in Rwanda after his then rebel force ended the brutal 1994 genocide by driving out Hutu fighters, that would mean talking to the Democratic Forces for the Liberation of Rwanda (FDLR).