From 1961 until 1991, Eritrea had fought a long war of independence against Ethiopia.
The Ethiopian Civil War began on 12 September 1974 when the Marxist Derg staged a coup d'etat against Emperor Haile Selassie.
It lasted until 1991 when the Ethiopian People's Revolutionary Democratic Front (EPRDF)-a coalition of rebel groups led by the Tigrayan People's Liberation Front (TPLF)-overthrew the Derg government and installed a transitional government in the Ethiopian capital Addis Ababa.
The Derg government had been weakened by their loss of support due to the fall of communism in Eastern Europe.
During the civil war, the groups fighting the Derg government had a common enemy, so the TPLF allied itself with the Eritrean People's Liberation Front (EPLF).
In 1991 as part of the United Nations-facilitated transition of power to the transitional government, it was agreed that the EPLF should set up an autonomous transitional government in Eritrea and that a referendum would be held in Eritrea to find out if Eritreans wanted to secede from Ethiopia.
The referendum was held and the vote was overwhelmingly in favour of independence. In April 1993 independence was achieved and the new state joined the United Nations.
In 1991 the EPLF-backed transitional government of Eritrea and the TPLF-backed transitional government of Ethiopia, agreed to set up a commission to look into any problems that arose between the two former wartime allies over the foreseen independence of Eritrea.
This commission was not successful and during the following years relations between the governments of the two sovereign states deteriorated.
The border between the two states became a major irritant, and in November 1997 a border committee was set up to try to resolve that specific dispute.
After federation and before independence the line of the border had been of minor importance because it was only a demarcation line between federated provinces and initially the two governments tacitly agreed that the border should remain as it had been immediately before independence.
However, on independence the border became an international frontier, and the two governments could not agree on the line that the border should take along its entire length, and they looked back to the colonial period treaties between Italy and Ethiopia for a basis in international law for the precise line of the frontier between the states.
Problems then arose because they could not agree on the interpretation of those agreements and treaties, and it was not clear under international law how binding colonial treaties were on the two states.
President Isaias Afewerki of Eritrea, realising that his influence over the government in Ethiopia was slipping and given that "the facts on the ground, in the absence of a concrete border being marked-which anyhow lost much of its relevance after 1962 when Eritrea was absorbed by Ethiopia-have eminent relevance to any borderline decision of today" calculated that Eritrea could annex Badme.
If successful this acquisition could be used to enhance his reputation and help maintain Eritrea's privileged economic relationship with Ethiopia.
However, because Badme was in the province of Tigray, the region from which many of the members of the Ethiopian government originate (including Meles Zenawi the former Ethiopian prime minister), the Ethiopian government came under political pressure from within the EPRDF as well as from the wider Ethiopian public to meet force with force.
After a series of armed incidents in which several Eritrean officials were killed near Badme, on 6 May 1998, a large Eritrean mechanized force entered the Badme region along the border of Eritrea and Ethiopia's northern Tigray Region, resulting in a firefight between the Eritrean soldiers and the Tigrayan militia and security police they encountered.
On 12 May 1998, Eritrean armed forces, composed of at least two brigades of regular soldiers, supported by tanks and artillery, attacked the town of Badme and several other border areas in Ethiopia's Tahtay Adiabo Wereda, as well as at least two places in its neighboring Laelay Adiabo Wereda.
On that day and in the days immediately following, Eritrean armed forces then pushed across the flat Badme plain to higher ground in the east.
Although the evidence regarding the nature of Ethiopian armed forces in the area conflicted, the weight of the evidence indicated that the Ethiopian defenders were composed merely of militia and some police, who were quickly forced to retreat by the invading Eritrean forces.
Given the absence of an armed attack against Eritrea, the attack that began on 12 May cannot be justified as lawful self-defense under the UN Charter.
On 13 May 1998 Ethiopia, in what Eritrean radio described as a "total war" policy, mobilized its forces for a full assault against Eritrea.
The Claims Commission found that this was in essence an affirmation of the existence of a state of war between belligerents, not a declaration of war, and that Ethiopia also notified the United Nations Security Council, as required under Article 51 of the UN Charter.
The fighting quickly escalated to exchanges of artillery and tank fire, leading to four weeks of intense fighting. Ground troops fought on three fronts.
On 5 June 1998, the Ethiopians launched air attacks on the airport in Asmara and the Eritreans retaliated by attacking the airport of Mekele.
These raids caused civilian casualties and deaths on both sides of the border.
The United Nations Security Council adopted Resolution 1177 condemning the use of force and welcomed statements from both sides to end the air strikes.
There was then a lull as both sides mobilized huge forces along their common border and dug extensive trenches.
Both countries spent several hundred million dollars on new military equipment.
This was despite the peace mediation efforts by the Organization of African Unity (OAU) and the US/Rwanda peace plan that was in the works.
The US/Rwanda proposal was a four-point peace plan that called for withdrawal of both forces to pre-June 1998 positions.
Eritrea refused, and instead demanded the demilitarization of all disputed areas along the common border, to be overseen by a neutral monitoring force, and direct talks.
With Eritrea's refusal to accept the US/Rwanda peace plan, on 22 February 1999 Ethiopia launched a massive military offensive to recapture Badme.
Tension had been high since 6 February 1999, when Ethiopia claimed that Eritrea had violated the moratorium on air raids by bombing Adigrat, a claim it later withdrew.
Surveying the extensive trenches the Eritreans had constructed, Ethiopian General Samora Yunis observed, "The Eritreans are good at digging trenches and we are good at converting trenches into graves.
They, too, know this. We know each other very well".
Following the first five days of heavy fighting at Badme, by which time Ethiopia had broken through Eritrea's fortified front and was 10 kilometers (six miles) deep into Eritrean territory, Eritrea accepted the OAU peace plan on 27 February 1999.
While both states said that they accepted the OAU peace plan, Ethiopia did not immediately stop its advance because it demanded that peace talks be contingent on an Eritrean withdrawal from territory occupied since the first outbreak of fighting.
By 23 May Ethiopia claimed that its "troops had seized vital command posts in the heavily defended Zalambessa area, about 100km (60 miles) south of the Eritrean capital, Asmara"] But the Eritreans claimed they withdrew from the disputed border town of Zalambessa and other disputed areas on the central front as a "...'goodwill' gesture to revive peace talks" while Ethiopia claimed it was a 'tactical retreat' to take away one of Ethiopia's last remaining excuses for continuing the war; a report from Chatham House observes, "the scale of Eritrean defeat was apparent when Eritrea unexpectedly accepted the OAU peace framework."
Having recaptured most of the contested territories-and having heard that the Eritrean government would withdraw from any other territories it occupied at the start of fighting in accordance with a request from the OAU-on 25 May 2000, Ethiopia declared the war was over.
By the end of May 2000, Ethiopia occupied about a quarter of Eritrea's territory, displacing 650,000 people and destroying key components of Eritrea's infrastructure.
The widespread use of trenches has resulted in comparisons of the conflict to the trench warfare of World War I.
This trench warfare led to the loss of "thousands of young lives in human-wave assaults on Eritrea's positions" The Eritrean defences were eventually overtaken by a surprise Ethiopian pincer movement on the Western front, attacking a mined, but lightly defended mountain (without trenches), resulting in the capture of Barentu and an Eritrean retreat.
The element of surprise in the attack involved the use of donkeys as pack animals as well as being a solely infantry affair, with tanks coming in afterwards only to secure the area.
The fighting also spread to Somalia as both governments tried to outflank one another.
The Eritrean government began supporting the Oromo Liberation Front, a rebel group seeking independence of Oromia from Ethiopia that was based in a part of Somalia controlled by Mohamed Farrah Aidid.
Ethiopia retaliated by supporting groups in southern Somalia who were opposed to Aidid, and by renewing relations with the Islamic regime in Sudan-which is accused of supporting the Eritrean Islamic Salvation, a Sudan-based group that had launched attacks in the Eritrea-Sudan border region-while also lending support to various Eritrean rebel groups including a group known as the Eritrean Islamic Jihad.
On 18 June 2000, the parties agreed to a comprehensive peace agreement and binding arbitration of their disputes under the Algiers Agreement.
A 25-kilometer-wide Temporary Security Zone (TSZ) was established within Eritrea, patrolled by United Nations peacekeeping forces from over 60 countries (the United Nations Mission in Ethiopia and Eritrea (UNMEE).
On 12 December 2000 a peace agreement was signed by the two governments.
On 13 April 2002, the Eritrea-Ethiopia Boundary Commission that was established under the Algiers Agreement in collaboration with Permanent Court of Arbitration in The Hague agreed upon a "final and binding" verdict.
The ruling awarded some territory to each side, but Badme (the flash point of the conflict) was awarded to Eritrea.
Both countries vowed to accept the decision wholeheartedly the day after the ruling was made official.
A few months later Ethiopia requested clarifications, then stated it was deeply dissatisfied with the ruling.
In September 2003 Eritrea refused to agree to a new commission, which they would have had to agree to if the old binding agreement was to be set aside, and asked the international community to put pressure on Ethiopia to accept the ruling.
In November 2004, Ethiopia accepted the ruling "in principle".
The Eritrea-Ethiopia Claims Commission holds that Eritrea violated Article 2, paragraph 4, of the Charter of the United Nations by resorting to armed force to attack and occupy Badme, then under peaceful administration by Ethiopia, as well as other territory in the Tahtay Adiabo and Laelay Adiabo Weredas of Ethiopia, in an attack that began on 12 May 1998, and is liable to compensate Ethiopia, for the damages caused by that violation of international law.
Both nations have been accused of supporting dissidents and armed opposition groups against each other.
Tensions coninue to remain high.
-In August 2009, Eritrea and Ethiopia were ordered to pay each other compensation for the war.
-In March 2011, Ethiopia accused Eritrea of sending bombers across the border.
In April, Ethiopia acknowledged that it was supporting rebel groups inside Eritrea.
In July, a United Nations Monitoring Group accused Eritrea of being behind a plot to attack an African Union summit in Addis Ababa, the capital of Ethiopia, in January 2011. Eritrea stated the accusation was a total fabrication.
-In January 2012, five European tourists were killed and another two were kidnapped close to the border with Eritrea in the remote Afar Region in Ethiopia.
In early March the kidnappers announced that they had released the two kidnapped Germans.
On 15 March, Ethiopian ground forces attacked Eritrean military posts that they stated were bases in which Ethiopian rebels, including those involved in the January kidnappings, were trained by the Eritreans.