
The People's Defense Units, also called People's Protection Units, is a mainly-Kurdish militia in Syria and the primary component of the Syrian Democratic Forces (SDF). The YPG mostly consists of ethnic Kurds, but also includes Arabs and foreign volunteers; it is closely allied to the Syriac Military Council, an Assyrian militia. The YPG was formed in 2011. It expanded rapidly in the Syrian Civil War and came to predominate over other armed Syrian Kurdish groups. A sister militia, the Women's Protection Units (YPJ), fights alongside them. The YPG is active in the Autonomous Administration of North and East Syria (Rojava), particularly in its Kurdish regions.

The Anti-Terror Units are the special forces of the Syrian Democratic Forces, consisting of the best trained and equipped members of the People's Protection Units (YPG) and Women's Protection Units (YPJ). They were led by the Syrian Kurdish commander Ali Boutan until his death. YAT is trained by United States special operations forces and the CIA.

Anna Montgomery Campbell, also known as Hêlîn Qereçox, was a British feminist, anarchist and prison abolition activist who fought with the Women's Protection Units (YPJ) in the Rojava conflict of the Syrian civil war. She was killed in Rojava by a Turkish Armed Forces missile strike.

The Democratic Union Party is a Kurdish left wing political party established on 20 September 2003 in northern Syria. It is a founding member of the National Coordination Body for Democratic Change, and is described by the Carnegie Middle East Center as "one of the most important Kurdish opposition parties in Syria". It is the leading political party among Syrian Kurds. The PYD was established as a Syrian branch of the Kurdistan Workers Party (PKK) in 2003, and both organizations are still closely affiliated through the Kurdistan Communities Union (KCK).

Michael Enright is a British actor who has played supporting characters in Pirates of the Caribbean: Dead Man's Chest and Old Dogs, as well as in several TV series including Agents of S.H.I.E.L.D., Law & Order: LA, CSI: Crime Scene Investigation, Cold Case, Criminal Minds: Suspect Behavior, and Castle, among others. In 2015, Enright joined the Kurdish People's Protection Units as a volunteer to fight ISIL. He is currently in exile in Belize.

Rojda Felat is a Syrian Kurdish senior commander of the Women's Protection Units (YPJ) and Syrian Democratic Forces (SDF), who has fought in the Rojava conflict since it began in 2012, and has led several major campaigns against the Islamic State of Iraq and the Levant (ISIL). A revolutionary feminist, Felat's stated goal is to achieve social transformation in the Middle East through the YPJ, "liberating the Kurdish woman and the Syrian woman in general from the ties and control of traditional society, as well as liberating the entirety of Syria from terrorism and tyranny".

Macer Gifford is the pseudonym of a British former currency trader who travelled to Syria to fight with the Kurdish YPG militia against the Islamic State group. He took his identity from National Hunt jockey Macer Gifford, the brother of four-time champion jockey Josh Gifford. He spent five months fighting with the YPG in 2015 before returning to the UK in 2015. In 2016 he completed a second tour with the YPG in Syria. Gifford has also given his name as Harry.
Haukur Hilmarsson was an Icelandic anarchist and political activist. He played a crucial role in initiating a movement for the rights of refugees in Iceland. He rose to prominence during the 2009 Icelandic financial crisis protests after climbing to the roof of the house of the Icelandic parliament, Alþingishúsið, and hoisting the flag of the Bónus supermarket chain on the building's flagpole. His arrest two weeks later resulted in an attempt by a crowd of protesters to storm the Icelandic Police headquarters in downtown Reykjavík where Haukur was held and from where he was subsequently released.

Ivana Hoffmann, also known as Avaşin Tekoşin Güneş, was an Afro-German feminist communist who fought with the Marxist–Leninist Communist Party (Turkey) (MLKP) in the Rojava conflict of the Syrian civil war. She was the first female foreign fighter in the Syrian Democratic Forces to die in the conflict.

The International Freedom Battalion, commonly abbreviated as IFB or EÖT, is an armed group consisting of leftist foreign fighters fighting for the People's Defense Units in the Syrian Civil War in support of the Rojava Revolution and against the Islamic State, the Turkish Armed Forces, and the Syrian National Army. The formation of the IFB was announced in June 2015 in Ras al-Ayn. Inspiration for the group came from the International Brigades of the Spanish Civil War. The political ideologies of the fighters include Anarchism, Marxism–Leninism, Hoxhaism, Maoism, and anarcho-communism.

Lorenzo Orsetti, also known as Orso and Tekoşer Piling, was an Italian anarcho-communist and antifascist from Florence who fought with the Syrian Democratic Forces in the Rojava conflict.

Nubar Ozanyan was a Turkish-born Armenian radical communist revolutionary, who served as a commander in the militant Communist Party of Turkey/Marxist–Leninist (TKP/ML). Fighting in several conflicts for the group, he eventually died in combat against the Islamic State of Iraq and the Levant during the Battle of Raqqa.

The Women's Protection Units or Women's Defense Units is an all-female militia involved in the Syrian civil war. The YPJ is part of the Syrian Democratic Forces, the armed forces of Rojava, and is closely affiliated with the male-led YPG. While the YPJ is mainly made up of Kurds, it also includes women from other ethnic groups in Northern Syria.

The Wrath of Olives operations room is an insurgent group that is active in Turkish-controlled areas of northern Syria.

The YPG International or People's Protection Units International is a military unit made up of foreign fighters in the Syrian Democratic Forces. It was created in December 2016 as the Antifascist International Tabûr (AIT) of the People's Protection Units (YPG). The unit is part of the Syrian Democratic Forces in the Syrian Civil War.