PRESIDENT Ali Abdullah Saleh is already boasting of his place in military history; how his campaign to reunify Yemen will become a model studied in textbooks. Such talk may be premature but his success so far has confounded many outside observers: Yemen has long been regarded as a graveyard for military ambitions.

What began as an all-out civil war close to Sana'a, the northern capital, has been reduced in six weeks to a rebellion centred on two cities, Aden and Mukalla in the south. Barring some dramatic development such as foreign intervention or insurrection in the north the end is probably only a matter of time.

Northern leaders insist that they do not aim to capture Aden (casualties on both sides would be too high) but say the current shelling is part of an attempt to force a surrender.

How long Aden can hold out economically depends largely on the willingness of outsiders to provide a lifeline. Piped water supplies are crippled, electricity is available only intermittently and the oil refinery is out of action. According to the United Nations, hospitals are filled to capacity and medical supplies are running out.

The city's population is swollen by people seeking refuge from outlying districts, and there are reports of unrest caused by Islamic militants.

These factors could combine to cause a public order problem which the city's fragile 'government' is unable to cope with.

The day-to-day difficulties of life are compounded by the question of how long Aden can hold out politically. The Democratic Republic of Yemen, proclaimed three weeks ago by the leader of the Yemeni Socialist Party, Ali Salem al-Baidh, has so far been a resounding flop.

Hopes of swift recognition by Saudi Arabia, Kuwait and other Gulf states failed to materialise, and as the territory controlled by the breakaway south dwindles, prospects for recognition fade.

It also looks less likely that the Socialists will now be able to play what many thought was their trump card: switching their new state from Aden to the oil-rich province of Hadramaut and bringing it quickly under the umbrella of the Gulf Co-operation Council. The president's forces started attacking the province's capital, Mukalla, at the weekend.

The breakaway state has had difficulty forming a government. Several of those named as ministers are abroad and only two - the vice-president and the defence minister - are actually in Aden. The choice of Abd al-Rahman al-Jifri, a non-Socialist opposition leader, as vice-president, was intended to demonstrate broad support, but he is widely perceived as a Saudi stooge and was promptly disowned by his own party, the League of the Sons of Yemen.

The separatists are only one element within the Socialist Party (though the dominant one at present) and a significant number of other prominent figures are keeping their heads down. Several have avoided the war altogether by contracting illnesses which forced them to seek treatment abroad.

President Saleh is relying on those Socialists who see nothing to gain and a lot to lose by prolonging the war. He has named 15 individuals he holds personally responsible for the war, thus inviting dissident Socialists to end the conflict for him by removing the ringleaders.