This WAS the Policy:
"The United States plans to maintain its military presence in northeastern Syria until 2021
for three reasons: to prevent the return of the Islamic State, to influence the political
transition in Syria, and to block the construction of the Iranian “land bridge” to the
Mediterranean. Because of this commitment, the United States decided to keep two
thousand men on the ground and to seek help from the Syrian Democratic Forces (SDF),
including the YPG, which is the military branch of the Democratic Union Party, usually
referred to as the PYD, or Partiya Yekîtiya Demokrat in Kurdish. (YPG, translated as People’s
Protection Units, stands for Yekîneyên Parastina Gel in Kurdish.) This decision provoked
a major crisis, as Turkey—historically a strong US ally—considers the YPG as the Syrian
branch of its decades-long domestic foe, the Kurdistan Workers’ Party (PKK). The United
States therefore faces a dilemma. On the one hand, the YPG is indispensable to the
military and political structure ruling northeastern Syria. On the other hand, without the
active support of Turkey, the American strategy of countering Iran and Russia is seriously
compromised. With the Turkish army’s offensive against the YPG, the United States
risks losing its indispensable local ally"
https://www.hoover.org/sites/defaul...al-strategy-cannot-ignore-local-reality_1.pdf