How did the border conflict begin?

The border between Ethiopia and Eritrea has been described as a geographer's nightmare.

It is a nightmare which became a reality as soon as the neighbours' once-friendly relationship turned sour.

From 1962 to 1993, Eritrea was ruled as a province of Ethiopia - and any argument over the borders was little more than a squabble between two local authorities.

So when Eritrea and Ethiopia separated amicably in 1993, no one paid too much attention to the details of the divorce settlement - least of all to a few hundred square kilometres of sparsely populated land in a region called Badme.

But when relations between the two neighbours deteriorated, Ethiopia accused Eritrea of invading a piece of land that was under Ethiopian administration.

The Eritreans replied that the land in question was rightfully theirs.

The result was a war fought on three fronts at the cost of tens of thousands of lives.

Who set up the boundary commission?

The commission was set up by the two countries as part of the Algiers peace settlement signed by both parties in 2000.

It followed a model that has been used in other cases around the world, where arbitration tribunals, instead of the International Court of Justice, have been used.

There are five lawyers - two nominated by each country - who then nominated a president of the commission who has the casting vote.

So what was the Commission's terms of reference?

Basically the commission was asked to interpret colonial treaties as the basis for the boundary.

This frontier was fixed in 1902 by a treaty between the Italian government, which had colonised Eritrea, and the Ethiopian Emperor Menelik II - ruler of what was then one of the few independent African states.

The border is approximately 900 km long, and contains some of the driest, hottest and most hostile territory in the world. Much of it is defined by rivers.

Most of the border area under dispute is largely uninhabited - barren land used as traditional grazing grounds by local people.

In terms of natural resources, the disputed area has virtually no value at all.

As for the demarcation, it will take into account the treaties signed between Ethiopia and Italy at the start of the 19th century, but these are not entirely clear, and contain elements that will be far from easy to interpret.

Some areas of both countries have been traditionally administered from each other's territory, and this will further cloud any decision on where the border lies.

What makes this task particularly difficult is that it means actually defining the line and producing a written definition of it or a map.

Also the demarcation is going to be very difficult because of the number of mines along the boundary.

What will the UN do if one or both countries reject the decision and new war breaks out?

Well, both countries have promised the UN that they will accept whatever decision is reached.

In theory, the commission's decision will be final and binding, with no right of appeal.

But clarification can be sought by both countries in the weeks ahead.

Both governments say they will accept what is decided in the Hague.

But it is no secret that local officials in the northern province of Tigray, from which the current government in Addis Ababa sprang, are openly opposed to the prospect of losing key border villages to Eritrea.

And if a new war breaks out there is very little the UN can really do.

For the last two years, the Ethiopian and Ertrean forces have been seperated by a narrow zone patrolled by 4,200 UN forces.

So if one side is unhappy with the outcome, there could be real pressure on the UN troops.

General Patrick Cammaert, who is in charge of the UN troops in the region, has warned that if the two countries decide to go back to war, the UN will simply pack up and go home.