The present secessionist war in Eritrea has been going on for 16 years but the strategic Red Sea province has, almost since the time of Christ, fluctuated between independence and some kind of affiliation with Ethiopia, to the south.

Eritea, about the size of Pennsylvania, forms one-tenth of Ethiopia's land area. But its sparse population of about 2 million is a much smaller proportion of Ethiopia's total of about 28 million.

The area that is now Eritrea once formed the Kingdom of Axum, which flourished from the 4th to 6th centuries and stretched across the Red Sea into the Arabian Peninsula. By the 10th Century, it was linked to the Ethiopian kingdom but it retained much of its independence until the rise of the Ottoman Empire.

For more than 300 years after that, Eritrea was under disputed control until it became a colony of Italy in 1890. Twice, Italy launched attacks against Ethiopia from Eritrea. In 1941, Britian liberated the colony and administered it until 1952.

In 1952, with American support but with opposition from the Soviet Union, Eritrea was federated with Ethiopia and 10 years later it was integrated fully within the Ethiopian Empire of Haile Selassie.

Because of its water shortage and poor rainfall, Eritrea traditionally has produced few crops, although modern irrigation has increased the production. Its chief usefulness to Ethiopia has been its two Rea Sea ports, Massawa and Assab, Ethiopia's only seaports.

As in Ethiopia itself, Moslems are believed to outnumber Christians in Eritrea, but the secessionist efforts have never been along clearcut religious lines.

Under Emperor Haile Selassie, who was overthrown in 1974 and died a year later, the government and the Ethiopian Orthodox Church were closely interwined and Moslem countries frequently claimed discrimination in the empire.

Haile Selassie was replaced by a Marxist military government, supported by the Soviet Union and Cuba, that has brought a Moslem orientation to the government.

The Eritrean secessionist struggle has been hampered by rivalry among nationalist factions.

The largest and oldest faction, the Eritrean Liberation Front, a Moslem-oriented, Arab-supported group, has frequently been at odds with the Eritrean People's Liberation Front, a more radical faction with Marxist backing. A third faction, headed by Osman Saleh Sabeh but apparently with the smallest following, reportedly is backed by Iraq.