U.S. Central Command Commander General Joseph L. Votel, the highest-ranking U.S. military official to visit Syria since the war erupted in 2011, came to Northern Syria in May 2016.
Kurdish forces established a stronghold about 37 kilometers (23 miles) north of Raqqa. ISIL reportedly used the residents of Raqqa as human shields, preventing them from leaving the city.
According to Joshua Walker of the German Marshall Fund, Raqqa could be "the beginning of the end" for ISIL, and the most important offensive since Kobani in 2015.
Preparations
On 20 May the US-led coalition dropped leaflets on the city, encouraging the residents to leave.
The SDF is led and dominated by YPG forces, which generally consist of Kurds. To avoid ethnic tensions with Raqqa's majority Arab population, US special forces trained more than 200 Arab fighters to take part in the offensive.
The announcement for the offensive was made on 24 May, when the 30,000-strong SDF announced the offensive, "with participation from all SDF units", mobilising thousands of fighters in the countryside north of Raqqa, with the aim of expelling ISIL fighters from north of al-Raqqa.
The US-led coalition stated that it would provide air support for the offensive. Russian foreign minister Sergei Lavrov announced that his country was ready to coordinate with U.S. and Kurdish forces in the offensive, but the U.S., distrustful of the Russian establishment, turned down the offer.
The offensive
On 21 May 2016 the SDF, led by the YPG, captured the village of al-Hishah, near the town of Ayn Issa in the northern countryside from ISIL, killing eight fighters. In the following days additional SDF fighters were mobilized from Tell Abyad to Ayn Issa. ISIL fighters in Raqqa responded by creating defensive lines and tunnels in the city. seven Coalition airstrikes on ISIL positions were confirmed on 23 May. On 25 May, the SDF took control of the Namrodia and Matmashraja villages near Ayn Issa.
On 26 May, the SDF reported new gains. SDF forces took the villages of Qartaja, al-Fastah, Indebin and Matmasraja. They had advanced some 6 km into IS-held lands north of Raqqa, and killed at least 31 ISIL fighters. By 30 May, ISIL had redeployed 2,000 to 3,000 militants to Raqqa, from Mosul and other areas controlled by ISIL. It was also reported that ISIL's use of civilians as human shields was slowing down the SDF advance. Later on the same day, the SDF captured an additional nine villages from ISIL, in the northern countryside of Raqqa.
Aftermath
On 3 June 2016, a YPG unit infiltrated into a detention center run by ISIS in Raqqa city and raided it, rescuing a number of prisoners, including a Yezidi family.
Syrian Democratic Forces
CJTF–OIR
Islamic State
Nuri Mahmoud (MFS commander)
Abu Bakr al-Baghdadi (Leader of ISIL)
United States special operations forces
Syrian Democratic Forces
CJTF–OIR
Islamic State
Rojda Felat (YPJ commander)
Nuri Mahmoud (MFS commander)
Abu Bakr al-Baghdadi (Leader of ISIL)
People's Protection Units (YPG, the leading group)
Women's Protection Units (YPJ)
Liwa Thuwar al-Raqqa
Army of Revolutionaries
Seljuq Brigade
Al-Sanadid Forces
United States special operations forces