WASHINGTON - President Donald Trump prepares to welcome Turkish President Recep Tayyip Erdogan to the White House on November 13, just weeks after Turkey launched an assault in Syria on Kurdish fighters -- longtime allies of the United States in the fight against Islamic State terrorists.
While the focus of the world last week shifted to the death of Islamic State (IS) leader Abu Bakr al-Baghdadi in a U.S. operation in northwestern Syria, Turkey has continued its attacks on the Kurds.
Erdogan has voiced his country's determination to continue the fight against terrorism in Syria in the aftermath of Baghdadi's death.
"The killing of Daesh's ringleader marks a turning point in our joint fight against terrorism," Erdogan said in a tweet Sunday, referring to al-Baghdadi's death.
"Turkey will continue to support anti-terror efforts - as it has done in the past. Having paid the dearest price in the fight against Daesh, PKK/YPG, and other terrorist organizations, Turkey welcomes this development," he added, referring to the IS group by its Arabic acronym.
Turkish police have detained more than 100 people suspected of links to IS since al-Baghdadi's death was announced.
But despite these efforts, experts said, Kurdish armed groups remain Ankara's main focus in its anti-terror campaign.
Turkey began a military offensive in northeast Syria on October 9 with a stated objective to clear the Turkey-Syria border area of a Kurdish armed group it views as terrorist.
The People's Protection Units (YPG) is the main force within the Syrian Democratic Forces (SDF), a Kurdish-led alliance that has been an effective partner of the United States in its fight against the Islamic State (IS) terror group in Syria.
Turkish officials say the YPG is an extension of the Kurdistan Workers' Party (PKK), a group based in Turkey that for decades has been engaged in an armed struggle with Turkish security forces for greater Kurdish rights in Turkey.
The PKK is designated as a terrorist group by Turkey, the United States and European Union.
Turkey vs. US priorities
Experts charge the multilayered Syrian conflict has led involved countries to prioritize their objectives and forge alliances based on their national interests.
"The root cause of this entire problem is that the PKK [and] YPG is a political problem for the U.S. It's an alliance management problem, but it's not a security threat," said Aaron Stein, director of the Middle East Program at the Foreign Policy Research Institute.
"For Turkey, the PKK is a national security threat, and if you reverse that, IS is a national security threat for the U.S., and for Turkey, it's a police problem," he added.
Michael Reynolds, an associate professor of Near Eastern Studies at Princeton University, said there has been a growing fear in Turkey that "the PKK/YPG would use northern Syria as a base and or safe zone from which it could wage armed struggle to drive out the Turks."
"This fear or concern is not a pet peeve or quirky obsession of Erdogan's. It is shared across the Turkish political spectrum," he told VOA.
Erdogan has often said that his country would not allow a "terror corridor" in northern Syria, referring to the region Syrian Kurdish fighters have carved up with the beginning of Syria's civil war in 2011.
Ankara has opposed U.S. support for the YPG since the beginning of the war on IS in 2014. But in the early years of the Syrian war, Turkey had other priorities, experts said.
"Turkey was alarmed at the early U.S. support for the YPG, but were more focused on (Syrian President) Bashar al-Assad," analyst Stein said.
Since the beginning of Syria's civil war in 2011, Turkey has been a major backer of Syrian rebels seeking to topple the regime Assad.
But as Assad has managed to regain control of much of the war-torn country, with the help of Russia and Iran, Turkey's priorities have allegedly shifted to accept Syrian regime forces on the northeast Syria border with Turkey if the YPG is removed.
Subsequently, Turkey launched an offensive in August 2016 to remove the YPG and IS from parts of the Turkey-Syria border region. It was the first time since the beginning of Syrian conflict that Turkey entered the country militarily.
Turkish forces and its allied Syrian rebels were able to capture several border towns from IS and YPG fighters.
As the war carried on, Turkey began another offensive against YPG fighters in the northwestern Syrian town of Afrin in January 2018, which had been under the YPG control since 2012.
Some analysts say the recent Turkish offensive in northeast Syria is a continuation of Ankara's policy to remove YPG from all border areas in northern Syria.
Peace talks factor
In 2013, the PKK declared a cease-fire to its operations against Turkish forces, which was followed by negotiations between the Kurdish militant group and Turkish President Erdogan's government.
Those talks had a direct impact on how Turkey viewed Syrian Kurdish groups that had ties with the PKK, experts said.
"When Turkey was holding peace talks with the PKK, Salih Muslim [a Syrian Kurdish leader linked with YPG] met with Turkish officials in Turkey, and the border was open," said Aliza Marcus, author of the book "Blood and Belief: The PKK and the Kurdish Fight for Independence."
But the YPG's political arm, the PYD, "was formed by the PKK more than a decade ago. However, it was always supposed to be a group focused on the situation of Syrian Kurds specifically, and it was operating only within Syria and to build self-rule for Syrian Kurds and others," she told VOA.
"The YPG has always been open about its desire for good relations with Turkey and had worked to ensure the border was quiet," she said.
What is next?
Following U.S. troop withdrawal from parts of northeast Syria, Syrian Kurds reached out to Russia for help in a bid to stop Turkey's military operations.
Russia was able to strike a deal with Turkey last week through which both sides will conduct joint patrols to ensure the removal of YPG from the border region.
"If the ostensible point of Peace Spring [Turkey's ongoing offensive in northeast Syria] was to push YPG off the border, they didn't really do that because the Russians took that to step in," Stein said.
However, regardless of how the situation in northeastern Syria will unfold, Turkey is determined to continue combating Syrian Kurdish fighters, experts assert.
"The endgame for Ankara is knocking the YPG down and off balance and blocking the Kurds from establishing anything that might resemble the nucleus of an independent Kurdish state or a safe sanctuary," analyst Reynolds said.
VOA State Department correspondent Cindy Saine contributed to this report.