Why didn't the YPG evacuate civilians before the Turkish operation?

Turkish President Recep Tayyip Erdogan signalled a military operation in northern Syria in late September while delivering his speech at the United Nations General Assembly. The plan became definite shortly after the US President Donald Trump announced the withdrawal of American troops from Syria on October 7, ending years of military support to the YPG, the Syrian branch of the PKK, which the US, EU and Turkey have listed as a terrorist organisation.

The operation began on October 9, coinciding with the anniversary of the PKK's lifelong leader Abdullah Ocalan’s expulsion from Syria. The Turkish fighter jets began hitting the border town, Ras al Ayn, a mixed town of Arabs and Kurds, and later moved to Tal Abyad, a strategic Arab-dominated town controlled by the YPG.

Turkey says its military operation is solely focussed on targeting YPG positions. The cross-border offensive has been named Operation Peace Spring and its Twitter handle posted on the morning of October 10 that the Turkish Armed Forces had "hit 181 terrorist positions with air forces elements and fire support vehicles".

For Turkey, there are two objectives of the operation: first, to create a 370km-wide and 32km-deep safe zone next to Turkey’s border; second, to relocate some of the 3.5 million Syrian refugeesTurkey has been hosting for several years. 

From the Turkish government's perspective, a safe zone can only be realised by clearing the area of the PKK/YPG, which has waged a terror campaign against the Turkish state for about 40 years, causing tens of thousands of casualties. The US began supporting the YPG from 2014, carving out a separate fighting unit from the YPG and rebranding it as the SDF. All this was one under the pretext of fighting Daesh, despite Turkey, a NATO ally, raising serious security concerns. 

In the past, when Russia engaged in aerial warfare against a large population of Syrians who rebelled against their autocratic leader Bashar al Assad, Turkey on several occasions negotiated a safe passage for civilians days before the start of Russian assault. The areas from where locals were evacuated included eastern Ghouta and Aleppo, which was besieged and bombed by the Syrian regime with Moscow's help. 

During his speech one day after the operation, Erdogan said Turkey guarantees that neither the Turkish army nor Ankara-backed Syrian National Army would harm civilians or properties belonging to them in northern Syria. 

“We promise, we commit ourselves,” he said. He also encouraged anyone who was forcefully conscripted by YPG  to leave the group. “We welcome them, whether they’re Kurds, Arabs,” he said.

According to Raqqa Slaughtered Silently, a non-violent activist group reporting from Syria, civilians were barred from leaving the area on the first day of operation. 

“SDF militia continues to prevent civilians from leaving the cities of Tal Abyad and Ain Issa in order to use them as human shields during military operations there,” the group said in a tweet.

The activists also claim Syrian Arabs were being used as “human shields” as the SDF forcefully recruited them to fight against Turkey, which has led to a loss of civilian lives of those embedded within SDF ranks.

The YPG has been previously accused of forcefully recruiting civilians, and denounced by human rights organisations for its child recruitment.