FACTBOX: Turkey to normalize ties with Armenia

(Reuters) - Turkey signed accords to normalize ties with Armenia in Switzerland on Saturday in a step toward ending a century of hostility.

Here are some details on why relations have been marred.

NAGORNO-KARABAKH

Turkey has kept its land border with Armenia closed since the early 1990s in protest at Yerevan's backing for ethnic Armenian rebels fighting for control of Nagorno-Karabakh, a region of Azerbaijan populated mainly by ethnic Armenians.

Turkey is a close ally of Azerbaijan and the two countries share close cultural and linguistic ties.

Some 30,000 people had been killed by the time the war ended in 1994 with Armenian forces occupying Nagorno-Karabakh and seven adjacent districts of Azerbaijan.

Turkey has said it hopes to open its border with Armenia by the end of 2009, but progress in the Ankara-Yerevan talks have been complicated by the Nagorno-Karabakh dispute.

SOME HISTORY

From the late 19th century, the Ottoman Empire's Armenian minority, numbering an estimated 2 million, began to assert nationalist aspirations and were backed by exile groups in the United States, Geneva and in the Georgian capital, Tbilisi.

Repression by Ottoman irregulars, mainly Kurds, led to the massacre of some 30,000 Armenians in eastern Anatolia in 1894-1896. Several thousand more were killed in Constantinople in August 1896 after Armenian militants seized the Ottoman Bank. Massacres were stopped after the Great Powers threatened to intervene.

WHAT HAPPENED IN 1915

As the Ottomans fought Russian forces in eastern Anatolia during World War One, many Armenians formed partisan groups to assist the invading Russian armies.

On April 24, 1915, Turkey arrested and killed hundreds of the Armenian intelligentsia.

In May 1915, Ottoman commanders began mass deportation of Armenians from eastern Anatolia thinking they might assist Russian invaders.

Thousands were marched from Anatolia toward Syria and Mesopotamia and Armenians say some 1.5 million died either in massacres or from starvation or deprivation as they were marched through the desert.

DIFFERING VIEWS

Ankara has said large numbers of both Christian Armenians and Muslim Turks were killed during the violent and chaotic break-up of the Ottoman Empire. A law in Turkey makes it a criminal offence to call the killings a genocide.

Armenia insists the killings should be declared a genocide. President Serzh Sarksyan said in a speech to mark Armenia's annual Genocide Day that securing international condemnation of the killings would be a priority for his administration.

Sources: Reuters/Dictionary of Twentieth Century History.