The Pentagon also advocates the continued equipping of so-called internal security forces that are in charge of security east of the Euphrates and the Syria-Iraq border. This would see the SDF's Kurdish factions link up with local security forces.

In March, the Pentagon decided to provide $300 million to back the SDF in fiscal year 2020. While the budget includes significant cuts in small arms support to the SDF, funding was increased by 45% for the group’s vehicles, including bulldozers needed to clear minefields and improvised explosive devices (IEDs) left behind by the Islamic State (IS).

There is, however, an issue that will impede cooperation: heavy weaponry supplied by the US Army to the Kurdish-dominated Syrian Democratic Forces (SDF). Weaponry such as tanks, armored personnel carriers and multiple rocket launchers have mostly been transferred to the People’s Protection Units (YPG) — a sister organization of the Kurdistan Workers Party (PKK), which Turkey and the United States consider a terrorist organization.

Turkish-American joint air and ground patrols have been in progress for a month in the areas east of the Euphrates, particularly between Tell Abyad and Ras al-Ain. Yet, in reality, even the lexicons of the patrols are not joint in nature. Ankara defines the ground operations as “joint efforts to establish safe zones,” while the United States calls them a “ security mechanism .” What is clear is that both armies intend to expand their efforts southward.

At a Sept. 18 press briefing, Chris Maier, the director of the Pentagon's task force to defeat IS, said the combined joint operations center in southern Turkey is fully operational. According to Maier, the center has removed YPG fortifications along the Turkish border and initiated the joint patrols.

However, Al-Monitor’s Jack Detsch, who attended the briefing, rightly posed the question of the day: Have Kurdish forces removed heavy weapons? And how far have the efforts to remove fortifications progressed?

Maier replied: “What we've committed to do is help to ensure the removal of the YPG elements and, as much as possible, ensure that that doesn't result in a security vacuum. Our assessment is that there are other security forces there that are local that are not YPG that would be part of an enduring security force, understanding that that may ultimately result in needing more forces that we would work with — with Turkey and — and others to address.”

The evasive reply points to an important reality. As US-Turkey joint efforts east of the Euphrates signal strong indications of a move southward, Washington is reaching a decision point: how to accommodate Ankara’s increasing pressure on the YPG to give up its heavy weaponry while also ensuring that this diminishing of the YPG's military capacity will not create a vacuum east of the Euphrates, particularly around Raqqa and Deir ez-Zor, where IS cells are located.

In short, the US Army’s cooperation with Turkey could mean retrieving the heavy weaponry from the YPG and minimizing the YPG’s operational capabilities. Yet the US Army is more compelled to maintain the YPG's capabilities given the threats of border security, counterterror operations against IS and fending off Russia-backed Syrian government forces and pro-Iran militias.

Although US-Turkey efforts along the border today appear to serve a purpose, such efforts are bound to fail as operations move southward.

It is obvious that Turkey will not offer concessions when it comes to disarming the YPG, even if the United States and Turkey move southward. This will force the United States to decide whether it will cooperate with the YPG or Turkey east of the Euphrates.

The US determination to upgrade the YPG’s military capacities has not been a secret for the past four years. According to Turkish media reports, between 2015 and 2019, the United States has delivered more than 20,000 trucks and hundreds of planes to equip an army of 110,000 troops in northeast Syria.

Through train and equip programs in the region, the YPG has drastically changed three fundamental domains: the space of armed conflict, the characteristics of armed conflict and the actors involved.

The US military has allowed the YPG to gradually develop its urban warfare capabilities, leading to the establishment of the YPG's new strategy of “urban guerrilla warfare.”

As military strategies shift from rural to urban, the YPG has developed a new set of capabilities that is transforming it into a regular army. Such capabilities include territorial control/area denial; conventional armor offensives and siege warfare through the use of armor warfare; sniper operations; indirect fire support; close air support; sophisticated military engineering for tunnel warfare; building defensive perimeters in urban warfare; IED and counter-IED operations; artillery and rocket fire support without line-of-sight availability; large-scale logistics movements; artillery-forward observation; surveillance and reconnaissance with unmanned aerial vehicles (UAVs).

The PKK’s effort to enhance its surveillance capabilities with UAVs include the US-made RQ-20 Puma and the civilian model DJI Phantom Drone.

According to Turkish media reports, the YPG has more than 100 surveillance drones and most of them are in use in Kobani, Tell Abyad, Ain Isa and Ras al-Ain.

Thanks to cooperation with the US military, the YPG is making the shift from rural guerrilla-style warfare to more conventional military strategies, such as territorial control and area denial through the use of armored warfare; siege warfare; indirect fire support; large-scale logistics movements; the conventionalization of existing military capabilities; acquisition of new capabilities in command, control and communication (C3); and information warfare.

The United States will have to make serious decisions as US-Turkish military efforts shift southward. Ankara is not likely to back down from its objections to the YPG’s enhanced military capacities. Most delighted with this development will be the Russia-backed Syrian government forces on standby in the Deir ez-Zor area as well as the pro-Iran Popular Mobilization Units currently in charge of border security on the Iraqi side.