BEIRUT — A two-pronged advance to capture key urban strongholds of the Islamic State group and its self-styled capital of Raqqa has underlined a quiet convergence of strategy between the U.S. and Russia to defeat the extremists, with Syria's Kurds emerging as the common link.
The dual advance toward Raqqa by the Syrian army from the southwest and the predominantly Kurdish Syria Democratic Forces from the north and west puts further pressure on the militants as they fend off simultaneous attacks on bastions such as Fallujah, and potentially Mosul, in neighboring Iraq.
The Kurdish involvement is proving vital to the interests of Washington and Moscow.
For the U.S., the predominantly Kurdish SDF has proven the most capable actor in northern Syria in defeating the extremist group, a point it made when its predecessor, the Kurdish YPG, held off the militants in Kobani, in 2015. That battle was seen by many as a turning point in the war on the IS group.
For Russia, the SDF advance has drawn IS fighters away from the front with the Syrian government and allowed the Kremlin's allies in Damascus to advance, showing that Moscow is participating in the battle against the IS group.
While the media has focused on the battles between Iraqi government forces and IS militants in the city of Fallujah, west of Baghdad, the Syrian army on Saturday reached Raqqa province for the first time in almost two years. The Syrian government has had no presence in Raqqa since August 2014, when IS overran the Tabqa air base and killed scores of government soldiers in a massacre they documented on video. The provincial capital, Raqqa, became the militants' first captive city.
Backed by intense Russian airstrikes, Syrian troops began their advance toward the province Wednesday, the same day that U.S.-backed SDF forces launched an attack on the IS stronghold of Manbij, which is 72 miles to the northwest of Raqqa and lies on a key supply route linking Raqqa with the Turkish border.
"In terms of direct coordination of activities on the ground, that is not happening," Pentagon press secretary Peter Cook said. "I know there have been discussions about changing that, but at this point, our position is the same."
Asked about it Monday, President Vladimir Putin's spokesman Dmitry Peskov told reporters: "We exchange information with the United States on a daily basis, twice a day, that's all I can say."
U.S. officials have consistently said that there are frequent conversations about flight safety issues and daily phone line checks to make sure the two nations can communicate quickly when necessary.
Lina Khatib, head of the Middle East and North Africa program at the Chatham House think tank, said it was hard to imagine such dual attacks on IS happening without prior agreement between the U.S. and Russia. Cooperation between the two global powers, which back opposing sides of the war, has marked the Syrian conflict in recent years.
"The Syria Democratic Forces is playing a complementary role to the (Syrian) army, and that is the product of a military agreement between Russia and the U.S. that is translating into a division of labor between the two forces on the ground," Khatib said.
To Christopher Kozak, Syria analyst at the Institute for the Study of War, the twin offensives show the government is being astute and taking advantage of the SDF offensive to improve its position on Raqqa.
"It's not a coincidence that these things are happening at the same time, but I would also not go so far as to say there's cooperation," Kozak said.
Syria's Kurds, who make up 10 percent of Syria's prewar population of 23 million, have played an outsized role in the civil war, now in its sixth year. The U.S. has struggled from the beginning to find moderate, effective partners in the chaos of the conflict, and the largely secular and cohesive YPG — the armed wing of the Kurdish PYD political party — has emerged as Washington's most trusted associate.
The Syria Democratic Forces — a mixed-religion anti-IS coalition made up of Kurdish and Arab groups — is dominated by the YPG. The U.S. provides critical air support to the SDF, and hundreds of U.S. special operation forces help train the group. Russia has also offered support to the Kurds, partly to gain leverage over Turkey, which considers the PYD to be a terrorist group.
In a way, the situation is a bit similar to the offensive on Fallujah in Iraq, where the Iraqi army works alongside Shiite militias against IS.
Both the Syrian and Iraqi armies do not have the capacity to be the sole actors in the battle against IS, and their external backers have incorporated the presence of non-state actors to provide military support.
The SDF denies coordinating with the Syrian government. But such dynamics are partly why the group is viewed with suspicion by other Syrian actors and the local population in Arab-majority areas.
Bassma Kodmani, a member of a Syrian opposition group known as the High Negotiations Committee, said the HNC is perplexed by the SDF's political position, saying the group sometimes attacks the Syrian army and sometimes fights on the same side.
"We have a player here that it's not at all clear what they stand for, what they want, what their ultimate agenda is — none of this is clear to us," Kodmani said. She added that such opacity creates outright hostility.
The perceived coordination between the SDF and the Syrian army is a potential problem for the U.S., because the Syrian government forces get more emboldened by each military victory against IS.
"The Obama administration is keen to demonstrate some form of achievement against the Islamic State before the end of the president's term, and in a way it seems that the focus on military achievement is overshadowing what happens the day after," Khatib said.
Raqqa is frequently targeted by the U.S.-led coalition, as well as the Syrian and Russian air force.
The battle for Raqqa is expected to be long and hard, with Syrian troops still about 45 miles (75 kilometers) away. Very few expect any real push toward the city anytime soon.
Kozak said the government is making a "low-cost investment" to position itself near Raqqa and "message its involvement in the ISIS campaign, to bolster its international credibility." The SDF has not been able to recruit enough Arab fighters, and the Kurds would rather focus on liberating areas in the Raqqa governorate that border Kurdish regions.
A Raqqa resident who fled it recently said the militants have dug trenches and planted mines around the city in anticipation of an attack. The resident, who spoke on condition of anonymity for fear of his safety, said the militants were well-prepared for what they perceive to be a "decisive battle," whether with the SDF or army troops.
--Associated Press writers Bassem Mroue in Beirut, Josh Lederman and Lolita C. Baldor in Washington and Nataliya Vasilyeva in Moscow contributed to this report.