The PYD shares the same ideology as the PKK terrorist group, and "consolidated an authoritarian regime in Syria, reliant on the Assad regime," according to a report by London-based think tank Henry Jackson Society.
Released on Thursday, the report titled "The Forgotten Foreign Fighters: The PKK in Syria" gives a detailed account of the PKK's background, and its fight against the Turkish government, as well as its relations with international actors.
"The PKK was uprooted from Turkey by the coup d’état of 1980 and took shelter in Syria, then-ruled by Hafez al-Assad, father of the current dictator, Bashar," said the report's author, Kyle Orton, a Middle East analyst and Research Fellow with the society.
"[...] and in the terrorist training camps of the Bekaa Valley [in Lebanon] the PKK was being prepared militarily by the Assad regime, the Soviet Union, and their Palestinian proxies," the report said.
Noting that the PKK launched its war against the Turkish state in 1984 "demanding outright independence," it said the group "established relations with other governments in the region to help sustain its insurgency in Turkey, notably with the revolutionary Islamist regime in Iran and to a lesser degree Saddam Husssein's Iraq".
The report also highlighted the "campaign of violence" waged by the PKK, that included "both targeted and indiscriminate aspects".
"Nurses, teachers, civil servants, and other “state agents” were murdered by the PKK, and, as always, a particular example was made of Kurds that opposed it.
"Turkish cities were attacked by PKK suicide bombers. Collective punishment was inflicted on villages that sided with the state and accepted money to construct militias that tried to keep the PKK out," it said, adding the PKK’s conduct amounted to crimes against humanity, according to human rights groups.
The report noted that the PKK was listed as a terrorist organization by the EU, NATO, and most Western governments, including the U.S., Australia, Britain, Canada, Germany, and the Netherlands, adding "This was not just done in solidarity with NATO ally Turkey, which of course also includes the PKK on its terrorism blacklist".
"The PKK has killed Western citizens in its attacks on tourist areas in Turkey and has kidnapped Westerners for ransom," it said.
The report also noted the PKK's "vast infrastructure" in Europe which it said was built to generate funds and raise support for the terrorist group, "based almost entirely around organised crime".
"By some estimates, the PKK's European wing brings in nearly £80 million per year by extorting the Kurdish diaspora, laundering money, and trading in narcotics, human beings, illegal weaponry, and more mundane items like cigarettes and tea," it said.
"This money is not only used to finance terrorism in Turkey, but finances acts of terror by the PKK in Europe itself, against Turkish state property, dissident Kurds, and other people and property deemed hostile by the PKK."
The report said the PKK began to rebrand itself in 2002, both "to try to avoid the terrorism designation and connotation in the War on Terror era – and for more local reasons relating to its various Kurdish audiences".
"The PKK adopted a 'confederal model', which meant creating ostensibly-local organisations: in Iraq the PKK created Kurdistan Democratic Solution Party (PCDK); in Syria the PKK created the Democratic Union Party (PYD) and an armed wing known as the People’s Protection Units (YPG); and in Iran the PKK created the Kurdistan Free Life Party (PJAK).
"PKK, PCDK, PYD/YPG, and PJAK are all officially parts of a transnational political umbrella, the Kurdistan Communities’ Union (KCK). The constituents of the KCK are not 'affiliates' or 'offshoots' or 'sister groups' of the PKK; they are organically integrated components of the same organisation – sharing membership, ideology, and a command structure under the ultimate authority of [jailed PKK leader] Abdullah Ocalan and his deputies in the PKK’s headquarters in the Qandil Mountains of northern Iraq," it said.
The report said that when the Syrian uprising broke out in 2011, the PYD attacked demonstrators and "retained conciliatory relations" with the Assad government.
"In the summer of 2012, Assad withdrew from the Kurdish-majority areas of northern Syria and set conditions – by among other things hosting the PKK for decades, allowing it to dominate the Kurdish political scene so as to divert its energies against Turkey and physically weakening other Kurdish organisations as it pulled back – that allowed the PYD to seize control of the vacated territory.
"This created clashes between the PYD and the anti-Assad rebellion, and diverted Turkey [...] into a secondary objective of securing its border against a PKK base," it said.
The report went on to say that the "PYD consolidated an authoritarian regime, heavily reliant on the Assad state, that viciously repressed all Kurdish political organisations and activists, including those with links to Erbil".
In 2014, the PYD/YPG received support from the U.S.-led coalition against Daesh after the battle at Kobani, it said.
"The coalition then continued to provide air support, money, weapons, and intelligence to displace IS [another acronym for Daesh] even in Arab-majority zones, enabling a rapid expansion of the YPG statelet in Syria.
"Since 2014, there has been a flow of people from outside the Kurdish areas to join the YPG in Syria. Of these several hundred foreign fighters, 29 have been killed," it added.
According to the report, most of the foreign fighters within the YPG are young and male and "Hardly any of them have ethnic Kurdish background, and very few of them show any prior links to the PKK – or indeed any form of militancy".
"More than 60% of the YPG foreign volunteers were under 30 and 80% were under 40. There was no noticeable pattern in the employment category of the YPG foreign fighters, with the exception of the military and students. The foreign YPG fighters are overwhelmingly male," it said.
"There are those who are unaware of the nature of the organisation they have joined beyond its media output," it added.
The report said that the movement of foreign fighters to the YPG "poses a series of questions – moral, legal, political and diplomatic – for Western governments, starting with if and how to prevent people joining the YPG/PKK and how to handle those who return after having joined this organisation".
It urged the British government to stop British volunteers joining the group.
"Allowing British citizens to go abroad to join a violent non-state actor with a record of war crimes is morally dubious, displacing onto foreign populations the risks of their misconduct, to say nothing of the danger these individuals expose themselves to, which the government should try to prevent," it said.
"Allowing European left-wing terrorist organisations to acquire training and experience in urban warfare from the PKK, as well as to forge transnational connections and to recruit among YPG volunteers, is deeply undesirable.
"The potential for such recruits to be drawn into lone-actor terrorism, whether individual or directed by a foreign terrorist organization, has to be taken seriously," it warned.
The report suggested an update to and amendment of The Foreign Enlistment Act, which it said could be an instrument to prevent British subjects being recruited by the YPG.
"The removal of passports, which are issued entirely at the discretion of the Home Secretary, is also an option for those cases where an intention to join the YPG is detected, and can certainly be applied to returnees," it said.
It also called for counteracting the "PKK’s deceptive propaganda on the nature of its project in Syria and its ability to recruit through its media platforms – whether television or social media".