U.S.-Backed Syrian Forces Eye Raqqa After Seizing Tabqa Dam From ISIS

A member of the US-backed Syrian Democratic Forces (SDF), made up of an alliance of Arab and Kurdish fighters, removes an ISIS group flag in the town of Tabqa, about 55 kilometres (35 miles) west of Raqqa city, on April 30, 2017. Delil Souleiman/AFP/Getty

The black and white flag of the Islamic State militant group (ISIS) being lowered over the rooftops of a liberated former stronghold is an increasingly familiar sight in Syria and Iraq over the last two years

On Wednesday, U.S.-backed coalition forces announced that they had fully seized the town of Tabqa and a key dam of the same name.

The strategic victories lay on the route to Raqqa, the jihadist group's largest Syrian hub, some 40 kilometers west of the city that serves as the de-facto capital of its self-declared caliphate.

The Syrian Democratic Forces (SDF), an alliance of Kurdish and Arab fighters, have battled ISIS in the area for weeks for control of the dam, and have finally driven all of its fighters from Tabqa town.

Their victory came: "Thanks to the sacrifices of the SDF's heroes and with the full, unlimited support of the U.S.-led international coalition," SDF spokesman Talal Silo told Reuters.

Brett McGurk, the U.S. special envoy for the global coalition fighting ISIS, tweeted confirmation of Tabqa's liberation. "Confirmed: ISIS defeated in Tabqa Dam and Tabqa City, now in hands of Syrian Democratic Forces, led by its Syrian Arab Coalition," McGurk wrote.

Read more: What to know about the coming battle for Raqqa

Tabqa dam, Syria's largest, is located along the Euphrates River and the jihadist group's control of its surrounding area had raised concerns about damage to the key piece of infrastructure and fears of possible collapse and catastrophic flooding.

The U.S.-led coalition is supporting the SDF with air power and special forces advisors in the battle for the dam, which was initiated by a daring raid behind enemy lines in March.

According to the coalition, ISIS has used the dam area as a key attack planning base.

Victory in Raqqa would be a critical success for both the international coalition and local ground forces. The city's liberation would release ISIS's stranglehold on a strategic location where it has had the time and space to plan international attacks, such as the November 2015 suicide bomb and gun assault in Paris.

The coalition estimated at the end of the March that "anywhere between 3,000-3,500 ISIS fighters" remained inside Raqqa, but would not provide an estimate on how many of those were foreign fighters that may attempt to return to their home countries.

The surrounding hills of Raqqa have served as the scene for gruesome beheading videos of western hostages—James Foley, Steven Sotloff, Peter Kassig, David Haines and Alan Henning. Inside the city, it has imposed its brutal brand of ultra-conservative Islamic law.

As the jihadist group prepares for the street-to-street battles for the city, it has allowed foreign fighter families to flee but prevented civilians from leaving the city.

It is a tactic the group has used in other strongholds it has lost, such as Manbij in northern Syria and Ramadi in western Iraq. As in the northern Iraqi city of Mosul, where an Iraqi coalition is battling ISIS for control, the group's fighters have likely fortified the city with booby traps, preparing to defend the city with suicide car bombs and sniper fire.

In February, America's top commander leading the fight against ISIS in Iraq, Lieutenant General Stephen Townsend, said Raqqa and Mosul would be retaken within six months. That estimate is likely to be extended due to the stiff resistance that ground forces are expected to encounter in central Raqqa, as they have in western Mosul.