The fight to recapture the Syrian city of Raqqa has officially begun. On June 6, the U.S.-backed Syrian Democratic Forces launched the fifth phase of Operation Wrath of the Euphrates, a direct assault on the Islamic State stronghold. Backed by U.S.-led coalition air support, the group began pushing toward Raqqa in November 2016 and has been advancing steadily on the city from the north, west and east. Composed of the Kurdish People's Protection Units (YPG) and the Syrian Arab Coalition, the Syrian Democratic Forces will face their toughest task yet, seizing the self-declared capital of the Islamic State.
If the eight-month battle for Mosul is any guide, the fight for Raqqa will not be easy. Islamic State fighters have had years to plan their defenses and entrench themselves in the city. The heavy use of mines and improvised explosive devises will slow and complicate the Syrian Democratic Forces' advance. Meanwhile, the YPG's participation in the assault has given the Islamic State propaganda leverage and helped it stiffen the resolve of its drafted recruits.
The Islamic State is not what it used to be, though. Years of punishing airstrikes, special operations' raids and continual fighting have depleted its forces and equipment. Lately, the effects of the ceaseless pressure on the extremist group have become more obvious. In the past couple of months, the Islamic State has lost vast swaths of territory in Iraq and Syria, including in the areas west of Mosul toward the Syrian border, and in the Homs and Hama provinces. Islamic State fighters have been practically driven out of Aleppo province just west of Raqqa province. And with Iraqi forces on the verge of seizing Mosul, the loss of Raqqa would come as a heavy blow to the Islamic State, whose fighters would have to retreat to their last significant redoubt along the Euphrates River Valley near the Iraqi border.
But first Raqqa has to be taken. Though the city is much smaller than Mosul, heavy fighting could drag on for months in the difficult urban setting. The estimated number of Islamic State fighters in Raqqa — 4,000 to 5,000 — is similar to the estimated number of Islamic State fighters in Mosul before that battle began in October, except this time they will be defending a more compact area. Given the firepower and the numbers arrayed against the Islamic State, however, it is highly unlikely it will be able to hold out indefinitely in Raqqa. Instead it is simply a question of how much time, and how many casualties, before the city is taken.