Oct 21 (Reuters) - Turkish Prime Minister Tayyip Erdogan called crisis talks that may authorise a cross-border military offensive into northern Iraq after Kurdish rebels killed 17 Turkish soldiers in an ambush on Sunday near the Iraqi border.

What is the story behind the tension? Here are some details:

* KURDISH HISTORY:

-- The Kurds are a non-Arab, mainly Sunni Muslim people, speaking a language related to Persian and living in a mountainous area straddling the borders of Armenia, Iraq, Iran, Syria and Turkey.

-- For most of their history they have been subjugated. In modern times Iran, Iraq and Turkey have resisted an independent Kurdish state and the Western powers have seen no reason to help establish one.

-- Kurdish nationalism stirred in the 1890s when the Ottoman Empire was on its last legs. The 1920 Treaty of Sevres, which imposed a settlement and colonial carve-up of Turkey after World War One, promised them independence.

-- Three years later Turkish leader Kemal Ataturk tore up the treaty. Kurdish revolts in the 1920s and 1930s were put down by Turkish forces. The Kurds were not recognised as a separate people or allowed to speak their language in public.

* FIGHT FOR A HOMELAND:

-- The Kurdistan Workers Party (PKK), named in 1978, took up arms against Turkey in 1984 with the aim of creating an ethnic homeland in the southeast. Since then more than 30,000 people have been killed in the conflict.

-- The ban on the use of the Kurdish language was lifted in 1991.

-- PKK leader Abdullah Ocalan was captured in 1999, tried and sentenced to death. This was reduced to life imprisonment in October 2002 after Turkey abolished the death penalty.

-- Fighting dwindled after Ocalan's capture, leading to a ceasefire and the withdrawal of rebel fighters from Turkey. Ocalan put new emphasis on seeking Kurdish rights through political rather than armed struggle.

* NORTHERN IRAQ:

-- The Kurds fared little better in northern Iraq where, under a British mandate, revolts were put down in 1919, 1923 and 1932.

-- Under leader Mustafa Barzani, the Iraqi Kurds waged an intermittent struggle against Baghdad after World War Two.

-- Kurdish northern Iraq won autonomy from Saddam Hussein with U.S. help in 1991, and has benefited from more than a decade of economic development. There has been some violence but it has not approached the levels seen in Baghdad.

* THE STRUGGLE CONTINUES:

-- Saddam's fall deepened the desire for autonomy and in September 2006 the president of Iraq's Kurdistan ordered the Kurdish flag to be flown on government buildings instead of the Iraqi national flag.

-- Some 3,000 PKK fighters are based in northern Iraq and launch attacks on security and civilian targets in Turkey. A few thousand PKK rebels are also believed to be inside Turkey.

-- Around 40 Turkish soldiers have been killed in fighting in the past month alone. Erdogan's government is under heavy domestic pressure to pursue the PKK into northern Iraq.

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