More than 1,000 refugees are fleeing into northern Uganda every day in expectation of the long awaited offensive, according to aid workers, and thousands more are moving inside southern Sudan. About 100,000 Sudanese are already in refugee camps in northern Uganda.
Aid workers have reported train- loads of military hardware travelling south to Wau and a 16-barge military flotilla sailing up the Nile towards Juba. It is thought that the government forces will try to take Nimule, the last important town still held by John Garang's rebel Sudan People's Liberation Army (SPLA), and cut it off from Uganda, its source of fuel and ammunition.
Although the World Food Programme says it has enough food in place in Uganda and Kenya to feed the victims of an all-out war in southern Sudan, there is little likelihood of a government 'victory' resulting in a peaceful settlement in which people would be able to return to their homes. Catastrophe would be followed by a drawn out guerrilla war and widespread insecurity creating a long-term refugee problem. According to the United Nations there are already 1,700,000 people displaced in southern Sudan and some 700,000 are facing famine this year.
In the past two years the government has retaken all the principal towns in the south and restricted the rebels to guerrilla warfare.
The hundreds of thousands living in camps around Nimule have fled from the fighting further north between the two factions of the SPLA. The movement split in August 1991 when the deputy commander, Riek Machar, declared a coup against Mr Garang but failed to unseat him. The rift was primarily over strategy: Mr Machar stands for independence for the south, while Mr Garang seeks more autonomy for the south within a united, secular Sudan. But the split divided the movement along tribal lines and both sides wreaked revenge on each other's homes and cattle, bringing starvation to many areas east of the Nile.
The fighting allowed the Khartoum government to launch its own offensive and win back large tracts of the south. It was also able to regain the support of some in the south who were disillusioned by the self-destruction of the SPLA.
There have been several attempts to reconcile the two factions but the rivalry between the two men gives little ground for hope that they could work together again. Mr Machar has the support of his Nuer people and some leading Dinkas who have fallen out with Mr Garang. He has access to supplies from Kenya but is said to be short of guns and ammunition. Mr Garang has these but appears to be losing support outside his own Dinka group, the Bor Dinka.
Both sides accuse the other of receiving help from the Khartoum government. A recent article in Africa Confidential predicts that Mr Machar will eventually win and says: 'As Garang's vision of a united secular country looks increasingly unlikely to southerners, they find an independent south looking more realistic.'
The question is whether they will bury their differences to defend what remains of strategic importance in their areas. Mr Machar's forces control most of Upper Nile province with the exception of Bor, Mr Garang's home town which is held by the government, and the area around Kongor which is held by Mr Garang's forces. The Garang faction controls most of Equatoria province except for the towns.