Kurdistan Workers' Party (PKK). The PKK has changed its name several times in recent years -- Kurdistan Freedom and Democracy Congress (KADEK) in 2002; Kurdistan People's Conference (KHK) in 2003; and Kurdistan People's Congress (KGK, or Kongra-Gel) in late 2003. In the spring of 2005, the group decided to revert to its original name. The PKK is also known as Halu Mesru Savunma Kuvveti (HSK).

PKK operates in southeastern Turkey, northern Iraq, northern Iran, Europe and the Middle East.

PKK's original goal was the establishment of an independent Kurdish state in southeastern Turkey. After a peace initiative was declared in 1999, PKK committed itself to using political means to promote rights for Kurds in Turkey.

It is estimated that PKK has up to 5,000 fighters, mainly concentrated in northern Iraq. The group has thousands of other supporters in southeastern Turkey and Europe.

Libya, Syria, Iran and Iraq gave modest aid to the PKK during the 1980s and 1990s. In the early 1980s, PKK guerrillas trained with Palestinian groups in the Beka'a Valley in Lebanon. PKK fighters also fought with Palestinian guerillas during the 1982 Israeli invasion of Lebanon.

The PKK is believed to get much of its funding from drug smuggling and extortion, though the group also receives money from charities, businesses and remittances from Europe.

Between intermittent periods of non-violence, PKK guerrillas have frequently bombed civilian and tourist targets as well as vandalizing buildings. PKK fighters also battle with village militia and Turkish military forces in southeastern Turkey.

The group also attacked Turkish diplomatic and business facilities in Western Europe in 1993 and 1995.

PKK's campaign became less violent in the 1990s. After Chairman Abdullah Ocalan's 1999 peace initiative, the group publicly committed itself to use political means to secure rights for Turkish Kurds. However, since the breakdown of the peace effort, PKK has resumed its militant activities.

Ocalan was captured in Kenya in early 1999. He was sentenced to death, but his sentence was commuted to life imprisonment after Turkey's Parliament abolished the death penalty in 2002. Ocalan is incarcerated on a prison island, where he is isolated from his former followers.

The PKK has established front organizations, under the coordinating organization known as the National Liberation Front of Kurdistan, to spread propaganda and increase its operational capabilities.

In the early 1970s, Abdullah Ocalan joined the Revolutionary Youth Federation, a student group dedicated to a leftist revolution in Turkey. Ocalan saw the liberation of the Kurds as more important than a general revolution. He established the PKK in 1974 to achieve this goal. During the next few years, Ocalan continued to organize while he studied theories of revolution. By 1978, PKK was set up in the Diyarbakir region in southeastern Turkey. However, Ocalan's group lacked significant funding, weapons or members.

The PKK confined its attacks to tribal chiefs in the province of Urfa until 1980, when it moved to the Beka'a Valley in Lebanon. PKK members trained with Palestinian militants there and later fought alongside them against the Israeli invasion in 1982.

During the 1980s, the PKK gained the financial support of Libya. Ocalan continued to consolidate power within the group and streamlined PKK's organizational structure. During this time, the PKK established the short-lived Kurdistan National Liberation Front in order to gain more political support from other Kurdish groups.

In the late 1980s and early 1990s, PKK expanded its military activities against the Turkish state. The PKK attacked Turkish security forces as well as the tourist industry.

By the late 1990s, the PKK campaign became less violent. The Turkish government also made significant gains in its efforts against the PKK, including the capture of Ocalan by special forces in Kenya in 1999.

In 2000, the PKK declared that it would seek only political means to ensure rights for Turkey's Kurdish population. However, that initiative failed when the PKK called off its unilateral cease-fire in 2004.

PKK is organized much like a traditional communist party. It is controlled from the top by the Chairmanship Council, which has acted as a collective presidency since the capture of Ocalan. The Central Committee is the main decision-making and executive body. The Central Disciplinary Committee is responsible for party discipline. The highest authority is the Party Congress, which meets every four years or upon demand of the chairman or the Central Committee. The structure of the PKK extends to the provincial and local level with a series of committees and cells.

PKK remained active through mid-2009, and the Turkish government responded with counter-attacks on PKK facilities. The PKK did propose a cease-fire in early 2009 and raised the possibility of a dialogue with Ankara.

The Kurdish cause was strengthened when an affiliated political party, the Democratic Society Party (DTP), gained some ground in the national legislature.

Nov. 17: A female PKK suicide bomber blew herself up near a police station in Yuksekova, in southeastern Turkey.

Nov. 27: An bomb exploded on a bus in central Turkey, killing four and wounding 17. The PKK was suspected.

June 29: A Turkish court sentenced Ocalan to death by hanging for committing treason.

July 20: A group of suspected PKK members opened fired on a restaurant in Caglayan, Turkey, killing one and wounding seven.

August: Ocalan declared a peace initiative, ordering PKK fighters to refrain from violence and requesting a dialogue with the Turkish government over Kurdish issues.

Sept. 3: A state security court commuted Ocalan's sentence to life imprisonment after Turkey repealed the death penalty.

Nov. 21: The deputy chief of the Turkish General Staff reported that a Washington and Ankara planned to disarm PKK fighters in northern Iraq.

September: Turkish forces engaged in several clashes with PKK rebels in southern Turkey. Some 70 rebels and 30 government soldiers died between June and September.

July 16: A bomb was detonated on a tourist bus in Turkey, killing five people. Turkish authorities said PKK members were responsible for the attack.

August: The U.S., Turkey and Iraq agreed to set up working groups to examine the issues involved in combating the PKK in Iraq. "It's the first time the United States has agreed to address the PKK threat in a military way," a U.S. official said. "This does not mean that Turkey has a green light to launch an attack on northern Iraq."

Aug. 20: PKK leaders implemented a one-month cease-fire, urging fighters to maintain passive defense positions to create an environment more conducive to negotiations with the Turkish government.

May: The U.S. State Dept.'s Iraq coordinator James Jeffrey reported that U.S. Ambassador to Iraq Zalmay Khalilzad had met with Iraqi Kurdish leaders to find ways to curb the presence of the PKK in northern Iraq. According to Jeffrey, fighting the PKK remained a top U.S. priority and would be addressed when the new Iraqi government was formed.

Aug. 28: A bomb in the Mediterranean resort city of Antalya killed three people and wounded 20. The Kurdistan Freedom Falcons claimed responsibility for the bombing and other recent explosions around the country.

Oct. 1: The PKK declared a unilateral cease-fire at the urging of Ocalan, but Turkish military leaders rejected the truce.

May-July: Turkey mobilized more than 100,000 troops near the southeastern border with Iraq in apparent preparation for an invasion against the PKK in northern Iraq.

Sept. 30: A dozen civilians were killed when PKK gunmen ambushed a minibus near Besagac in southeastern Turkey.

Oct. 7: PKK fighters killed 13 Turkish soldiers in fighting in southeastern Turkey. Two more were killed in a bombing the next day.

December: Turkey began a series of limited air and ground incursions into northern Iraq to strike suspected PKK bases.

February: Turkey launched a significant ground operation against PKK operations in northern Iraq. Officials confirmed that as many as 8,000 troops participated in the operation. The government reported that 24 PKK militants and five soldiers were killed in various clashes.

July 27: Turkish officials claimed that the PKK was responsible for an attack in a residential area of Istanbul. Two bombs exploded in the Gungoren neighborhood, killing 17 persons and injuring more than 150 others.

Aug. 19: The PKK and an affiliated group, the Kurdistan Liberation Hawks (TAK), claimed responsibility for a car bomb attack at a Mersin police checkpoint.

Aug. 23: PKK acknowledged it was behind a car bomb attack in a residential district of Izmir.

Oct. 4: PKK operatives attacked a Turkish military outpost at Aktutun. The attack resulted in the deaths of 15 soldiers and nine PKK militants.

Nov. 21: PKK claimed responsibility for bombing the Turkish side of an oil pipeline that connected Iraq's northern oil fields to the export facility in Ceyhan.

May: The PKK's acting leader, Murat Karayilan, suggested several methods for resolving the Turkish-Kurdish issue. He noted in an interview that one avenue could be negotiations involving Abdullah Ocalan, the head of the PKK who has been in prison for nearly a decade. He asserted that the PKK was probably undefeatable in military terms, and that the government should seek a proper forum for resolving Kurdish issues.

May 30: The U.S. Embassy in Turkey condemned the PKK for an attack on Turkish soldiers in Hakkari on May 28. The troops were killed when a military vehicle ran over a land mine.

June 3: The PKK said it would extend a "cease-fire" policy through mid-July 2009, but would still reserve the right to take "defensive" actions, if necessary. The cease-fire declaration followed statements by the government that it was committed to resolving the conflict with the Kurds. One PKK source said the group had dropped its demand for Kurdish independence, and was seeking local autonomy. The government reiterated that it would not negotiate with terrorists.

June 7: Turkish military aircraft attacked Kurdish militant positions in northern Iraq. Military sources said at least four aircraft participated in the attack after PKK fighters were seen in Iraqi territory near the Turkish border.