How many countries in the world share frontiers with nine other states? The massive Democratic Republic of Congo (formerly Zaire) borders Angola, Burundi, the Central African Republic, Congo-Brazzaville (the People's Republic of Congo), Rwanda, Sudan, Tanzania, Uganda and Zambia. It is this bizarre political geography of central Africa that, in part, determines its recent political upheavals.

The lunacy of colonial era carve-ups of sub-Saharan Africa territory bequeathed its peoples a legacy of violent secessionism continuing into the present. Whole ethnic groups were divided across arbitrary borders, breeding resentment and irredentist claims for decades to come.

During the 1960s wave of independence in the continent, most African leaders drew an unpalatable conclusion: any attempt to redraw the colonial boundaries would open the floodgates to a deluge of competing claims. These leaders feared a kind of African "domino theory" of successive crises in state legitimacy.

The driving ideologies would differ - ethnic-nationalist rather than Marxist (as in the original US domino theory of communist revolution) - but the repercussions for neighbouring states would be just as far-reaching: overwhelming and countervailing claims to redraw Africa's political map.

The present civil war raging in the DR Congo provides ample evidence of both the continuing desire to redraw boundaries, and of the determination of regional powers to prevent that at all costs. The fighting began at the start of August, when troops in the eastern provinces of Kivu North and South mutinied, quickly taking the major towns of Goma, Bukavu and Uvira, and then following up with a daring airborne strike on the far western ports which service the capital, Kinshasa.

President Kabila had only recently celebrated one year in office after coming to power at the head of a rebellion backed by many of the neighbouring powers: principally Rwanda, Uganda, and Angola. His victory had seemed the next step in an informal but powerful emerging politico-military alliance which connected Eritrea, Ethiopia, Uganda, (the South Sudanese provisional government), Rwanda, the new DR Congo and Angola, in a broad stripe across the entire continent.

Just a year later this supposed alliance of like-minded leaders is in disarray. Ethiopia and Eritrea have themselves been at war over borders; meanwhile, Kabila's regime in Congo was already seen to be isolated when in May the presidents of Uganda, Rwanda, and Angola ignored their invitations to attend the first anniversary celebrations of Congo's "liberation".

Kabila's subsequent order expelling all "foreign soldiers" from Congo's territory proved the trigger for the recent uprising itself. The backing of Rwanda and Uganda for the latest fighting - officially denied, but widely credited - leaves no doubt that the regional alliance is in tatters.

Many Congolese and several international commentators interpret Rwandan and Ugandan military backing for the anti-Kabila rebels as an attempt to redraw the very boundaries of post-independence Congo. Many Banyarwanda (Rwandan language-speaking ethnic Tutsis and Hutus) live in the Kivu provinces that border Uganda, Rwanda and Burundi, and have enjoyed ambiguous relations with the Congolese state.

In addition, severe population pressure on limited land in Rwanda may be influencing a hard-line tendency there to push for an annexation of eastern Congo to provide more territory for this tiny, but powerful, country to expand.

But the opening up of the question of any border's viability inevitably exposes all other regional states to the same questions. Angola - only a year ago Rwanda's ally in the Congolese "liberation" - has spoken harshly of irresponsible Rwandan actions which "dangerously destabilise" the entire Central African region. Zimbabwe, far to the south, has made even stronger noises of criticism. Both countries have backed up their words with troops. Angolan military strikes, in particular, appear to be turning the tide rapidly against the rebels.

Invading across their common border, Angolan military troops are reported to have cut off the supply lines of the rebel forces heading for the Congolese capital. A newly-confident President Kabila claims that there is only "mopping up" left to do; but the battle for ultimate control of Kinshasa is sure to be bloody.

In response to the heavy Angolan intervention in Congo, the Rwandan government has now publicly threatened its own intervention on the side of the rebels, a statement which in reality means an escalation from what is already a large military commitment and a strengthening of their hold on the east of the country.

Why should the Angolans have decided to reverse position and come out against their former Rwandan allies? The reasons are complex, but lie in Angola's own civil war, ongoing (with occasional periods of uneasy peace) for nearly 30 years.

A complete success by the Congolese rebels was always improbable in the short run. President Kabila, if chased from Kinshasa, would likely have holed up in his stronghold, the south-eastern province of Shaba (formerly Katanga, the site of a bloody secessionist war in 1960, rich in minerals and still having independent tendencies). He could, in principle, have prosecuted a deadly secessionist war from there.

The thought of a "Balkanised" Congo fills Angola with dread: such anarchy would provide the perfect platform for strengthened raids by Angola's rebel UNITA movement from across their shared frontier. More than anything else it is the fear of trouble next door that has triggered Angola's actions.

Yet it might be argued that just such a fear also drove the Rwandans and Ugandans to support the rebel forces in DR Congo this time. Their borders with the DRC have been troubled for a number of years by bands of militia that cross to commit massacres. The Rwandans, in particular, consider the Kivu provinces in the eastern Congo to have become effective safe havens for many of the Interahamwe killers from the 1994 genocide in their country.

Rwandan support for Kabila last year represented, in part, a desire for a strong man at the Congolese helm who would crack down on the Interahamwe. Kabila promised something of the sort, but was unwilling or unable to deliver in the time allotted. The present Rwandan/Ugandan tactics may be to establish a buffer zone in eastern Congo from which they will be hard to dislodge, protecting their own populations from insurgent attacks through strict military control.

Or, as many African leaders suspect, Rwandan involvement may represent a wholesale attempt to redraw existing national boundaries. Certainly the involvement of many regional powers in what is otherwise a Congolese domestic squabble indicates the strong fear that this is so.

Nelson Mandela's attempts at South African mediation in an increasingly regional war reflect his alarm that without a quick solution to the fighting more and more neighbours will be drawn in, seeing their own interests threatened by any challenge to the sovereign integrity of the Congolese giant. The African domino theory of successive revision of colonial boundaries continues to determine the destinies of that continent's peoples.

Stephen Jackson is director of the International Famine Centre at NUI Cork