FACTBOX: Tension over Kurds on Turkey-Iraq border

(Reuters) - The Turkish army carried out an "intense intervention" against Kurdish rebels in northern Iraq on Saturday, sending in special forces a day after the cabinet authorized a cross-border operation.

Following are some of the details behind the tension:

* 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 recognized 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 nearly 40,000 people have been killed in the conflict.

-- The Kurdish language ban was lifted in 1991.

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

-- Fighting eased 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 quashed 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.