Ankara settled on a nationalistic, tit-for-tat response, imposing tariffs on US products, including cars, alcohol and tobacco. “We will boycott US electronic products ,” Turkish President Recep Tayyip Erdogan said on Aug. 14. “If they have [the] iPhone, the other side has Samsung. In our country, there is Venus, Vestel.”

After President Donald Trump on Aug. 10 ordered the doubling of steel and aluminum tariffs on imports from Turkey over Brunson’s detention, the troubled Turkish lira took an additional hit. The lira has lost some 40% of its value since last year due to various factors. This has put Turkish businesses and consumers alike under pressure in a foreign-dependent economy with an inflation rate exceeding 15% . The current exchange rate is around 6.00 lira to the dollar , an improvement from its slide to 7.23 on Aug. 12.

These statements come as the US and Turkish militaries ramp up preparations for the final assault on IS in eastern Syria but also amid diplomatic tensions between the two NATO allies and professed strategic partners. Their partnership has been tested by a number of issues, including US support for the Syrian Kurdish People’s Protection Units (YPG), which Ankara considers a “terrorist” offshoot of the PKK, Turkey’s purchasing of S-400 missile defense systems from Russia and now the trial of Andrew Brunson, an American pastor who has been detained for nearly two years in Turkey.

The State Department has also asserted that the shared determination in the fight against IS carries on despite Turkish-US relations facing the worst of times in recent history. State Department spokesperson Heather Nauert told Al-Monitor, “While we work to resolve other matters in our relationship with the government of Turkey, we have not seen any change in our shared determination to see [the Islamic State] defeated.”

Combined efforts to defeat the Islamic State (IS or ISIS) and address Turkey's legitimate security concerns involving the outlawed Kurdistan Workers Party (PKK) remain in tact, Pentagon spokesperson Eric Pahon has told Al-Monitor. “Our military-military relationship [with Turkey] continues unaffected,” Pahon said.

While footage emerges of furious Turks burning dollars and smashing iPhones, the US and Turkish militaries are preparing for a new phase in the coordinated fight against IS in northern Syria, in Manbij province.

The fight against IS has a number of branches. For the United States, the town of Manbij is but one part of a bigger plan, but for Turkey, Manbij represents a “threat,” a national security concern, because of the YPG’s presence there.

For years, the YPG, the main component of the US-backed Syrian Democratic Forces (SDF), fought on the frontlines against IS, including helping liberate the IS stronghold of Raqqa last fall. Turkey, however, has accused the United States of aiding terrorists.

In June, the two countries came together and brokered a deal, or road map, for the YPG to leave Manbij, as Turkish forces, along with allied Free Syrian Army militias, continued a military operation in Afrin against the YPG. Now, despite their troubled relations, both sides say the Manbij process carries on, uninterrupted, mainly with patrols on the periphery of the city.

“The US and Turkish governments remain committed to implementing the road map to maintain security and stability in Manbij,” Pahon said. “The coalition will continue to work in close coordination with partner forces to deliver a lasting defeat of [the Islamic State], which remains a significant threat to the region and the world.”

Ankara has voiced similar dedication, but without reference to the battle against the Islamic State. “The process continues without a hitch,” Turkish Foreign Minister Mevlut Cavusoglu told reporters Aug. 19. “We are entering a joint patrol period.”

Since mid-June, Turkish and US forces have conducted 34 independent, but coordinated patrols along the military demarcation line outside Manbij city. Before the joint patrols can begin, Pahon said, “We still have a few details to work out. We remain committed to beginning interoperability training for combined patrols as soon as possible.”

For the United States, the Manbij operation is seen as sustaining coalition momentum for IS' ongoing defeat in the east. “The enduring defeat of [the Islamic State] is a top priority of this administration and of the State Department,” Nauert said. “Our diplomats are working closely with [the Pentagon] to support upcoming operations in eastern Syria by the [SDF], and with coalition capitals to support stabilization initiatives that enable Syrians to voluntarily and safely return to their homes in Raqqa and other former [Islamic State] strongholds.”

According to Selim Can Sazak, an adjunct fellow at the Century Foundation, a New York-based think tank, Turkey is concerned about IS because it conflicts with its national interest in the region, “although it is not a big priority for Turkey as it is for the US”

Since the launch in 2014 of Operation Inherent Resolve — the US-led military campaign to defeat IS — the extremist group’s control over land in Syria and Iraq has been significantly reduced. In July, the SDF completed the second phase of Operation Round Up, the effort to clear IS from eastern Syria. The next target is a small patch of land that IS holds near the Euphrates valley. The IS fighters are holding out in the city of Hajin, in eastern Syria, near the Iraqi border, said British Army Maj. Gen. Felix Gedney, deputy commander for strategy and support for the coalition.

The current challenge lies in spotting the 1,000-1,500 IS fighters left. “One issue we found is that ISIS had robust tunnels and some left by oil companies to store supplies, and ISIS fighters were living in the tunnels with food and water,” Col. Sean Ryan, a spokesman for Operation Inherent Resolve, told the Jerusalem Post. Some have also escaped to neighboring states or to the regime-controlled areas of western Syria, according to Ryan.

As Washington continues its cooperation with the SDF for the final strike on IS, during which it will mainly provide expertise and air support, Ankara claims the tariffs against Turkish imports are “self-defeating” given shared US-Turkish national security interests.

“The economic sanctions Mr. Trump’s administration is imposing on Turkey are poised to disrupt any atmosphere of cooperation — all while global threats demand that we strengthen, not weaken, the ties that bind us together,” Cavusoglu said in an Aug. 20 op-ed penned for USA Today.

The US Air Force base at Incirlik plays a role in this cooperation, and Turkish social media users have rallied for closing it, especially since the lira’s precipitous drop. Cavusoglu wrote in his op-ed, “Turkey’s Incirlik Air Base hosts American troops who are serving on the frontlines of the fight against ISIS. It has been a critical staging ground, putting allied forces hours closer than other bases in the region and has made a substantial difference in the ability to successfully root out ISIS.”

Cavusoglu did not touch on the future of the base, but the Pentagon says it is here to stay. “The United States is not leaving Incirlik Air Base in Turkey,” Pahon said. “The US presence in Incirlik, with the permission of the government of Turkey, has been a symbol of our commitment to work with and help defend our ally and strategic partner for decades.”

Ankara also puts the strategic partnership before any spat, Sazak said. He quoted an unidentified aide close to Erdogan as saying, “[That] our shared national security interests will get us through politically challenging times is the perspective here.”