ADDIS ABABA (Reuters) - Eritrea’s President Isaias Afwerki was due to arrive in Ethiopia on Saturday to cement a stunning rapprochement between the neighbours that has swept away two decades of hostility in a matter of weeks.

FILE PHOTO: A police officer walks past the flags of Ethiopia and Eritrea ahead of Eritrea's President Isaias Afwerki's visit to Addis Ababa, Ethiopia July 13, 2018. REUTERS/Tiksa Negeri/File Photo

The countries’ armies have been facing off across their border since a two-year war broke out in 1998 over territory and other disputes, claiming the lives of an estimated 80,000 people.

Full-scale fighting ended in 2000 with the signing of a peace deal but tensions burned on after Ethiopia refused to accept a boundary commission’s ruling over a border town.

Then Ethiopian Prime Minister Abiy Ahmed took office in April this year, announcing a series of sweeping reforms and, soon after, plans to mend ties with Eritrea.

Isaias’ visit comes less than a week after Abiy visited Eritrea’s capital Asmara to sign a pact that declared an end to their “state of war”.

The following is a timeline of the Horn of Africa countries’ relations:

* 100 AD to 10th century - Modern-day Eritrea was part of the Axum Empire, which in its heyday dominated the Red Sea coast and vast stretches of the Horn of Africa. It was one of the earliest Christian kingdoms after its rulers converted during the 4th century.

* 1890 - Italy formally creates a colony from a thin and craggy swathe of land along the Red Sea and names it “Eritrea” - an Italianized version of a Greek word that means “red land”. Rome uses it as a launchpad to invade Ethiopia six years later but its troops are routed by Emperor Menelik’s forces in the town of Adwa, the first defeat by a black African army of a European empire.

* 1935 - Eritrea remains an Italian colony for another four decades. But to avenge the debacle of Adwa, Italy’s Fascist dictator Benito Mussolini launches a full-scale invasion of Ethiopia. With the support of British troops, Ethiopian soldiers enter the capital Addis Ababa in 1941, marking the end of the occupation.

* 1952 - Eritrea is officially federated with Ethiopia two years after the United Nations approved a resolution backing a bid by Emperor Haile Selassie, despite some calls for a referendum.

* 1962 - Haile Selassie dissolves the arrangement and annexes Eritrea. A year earlier, a small group of Eritreans launched the war for independence that stretched for three decades.

* 1991 - The rebel Eritrean People’s Liberation Front led by Isaias Afwerki captures Asmara, having fought Ethiopia’s military leader, Mengistu Haile Mariam, alongside rebels from the Ethiopian People’s Revolutionary Democratic Front (EPRDF) led by Meles Zenawi. The EPRDF invades the Ethiopian capital of Addis Ababa and topples Mengistu.

* 1993 - Eritrea formally secedes from Ethiopia after a referendum and Isaias Afwerki is appointed president. The Red Sea state initially enjoys warm ties with Ethiopia, which is led by Prime Minister Meles Zenawi and is dominated by his TPLF group for the next two decades.

* 1998 - After two years of tensions over trade and other issues, clashes break out along the border over ownership of the disputed town of Badme, before evolving into a full-scale war. More than 70,000 Ethiopian citizens of Eritrean origin are expelled from Ethiopia.

* 2000 - A peace agreement is signed, brokered by the Organisation of African Unity - the precursor of the African Union - with both sides agreeing to accept an arbitration ruling. An estimated 80,000 people are thought to have died during the two-year war.

* 2002 - A Hague-based boundary commission hands Badme to Eritrea, but Ethiopia calls for dialogue and says it wants to hold discussions with Asmara before implementing the ruling, which Eritrea rejects. A standoff prevails.

* 2012 - Ethiopian prime minister Meles Zenawi, Eritrea’s former ally-turned-foe, dies.

* February 2018 - After three years of street unrest and violent protests, Meles’ successor, Prime Minister Hailemariam Desalegn, resigns in what he describes as a bid to smooth reforms.

* April 2018 - Former army officer Abiy Ahmed is appointed as Ethiopian premier and vows to seek peace with Eritrea. In June, the 41-year-old announces that Ethiopia would honour the provisions of the 2000 peace deal and the boundary commission ruling delivered two years later. He visits Asmara a month later and signs a pact on the resumption of ties. The two nations declare an end to their “state of war”.

(Removes reference to incorrect ethnic group in paragraph 13)