Issues dividing neighbors Armenia and Turkey, which announced Monday they would establish diplomatic relations for the first time:
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GENOCIDE: Bitterly divided by killing of up to 1.5 million Armenians by Ottoman Turks during World War I, which many scholars consider first genocide of 20th century. Armenia wants it recognized as one of worst humanitarian atrocities. Turkey denies it constituted genocide, contending toll has been inflated and dead were victims of civil war and unrest that killed Muslims as well as overwhelmingly Christian Armenians.
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NAGORNO-KARABAKH: Disagree over Nagorno-Karabakh, predominantly ethnic Armenian region of Azerbaijan controlled by separatists. Turkey closed border with Armenia in 1993 in solidarity with ally Azerbaijan, with which Turks share common language, culture and religion. Move hurt landlocked Armenia's economy.
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SLAYING OF TURKISH DIPLOMATS: Relations strained by murders of dozens of Turkish diplomats in 1970s and '80s by extremists seeking to expand Armenian homeland in eastern Turkey and vengeance for slayings of Armenians by Ottoman Turks. Militants also attacked Turkish Airlines counter at Paris's Orly Airport in 1983, killing eight people and wounding 56.