The Manbij offensive, code-named Operation Martyr and Commander Faysal Abu Layla by the SDF, was a 2016 military offensive operation by the Syrian Democratic Forces (SDF) to capture the city of Manbij from the Islamic State of Iraq and the Levant (ISIL), and eventually, the ISIL-held areas through Al-Bab to Herbel, in the area referred to as the "Manbij Pocket" in the northern Aleppo Governorate. The main goal of the offensive was to cut off ISIL's last supply routes from Turkey, and to prevent ISIL fighters from escaping across the Syria-Turkey border. For the first five days of the offensive, the US-led coalition conducted over 55 airstrikes in support of the SDF. After capturing Manbij city on 12 August, the SDF announced that the offensive would continue until the whole countryside around Manbij was captured, though the offensive effectively ended shortly after the Turkish Armed Forces initiated Operation Euphrates Shield to prevent the SDF uniting the regions of Rojava.
Preparations
In late December 2015, the SDF captured the Tishrin Dam and crossed the Euphrates, capturing the town of Tishrin and other nearby areas from ISIL, paving the way for a future offensive toward Manbij.
By 30 March 2016, the United States Air Force had conducted 25 airstrikes against the Islamic State. On 2 April, six non-YPG factions of the Syrian Democratic Forces (SDF) formed the Manbij Military Council (MMC) in preparation for the attack on Manbij. Most of the groups were part of the Northern Sun Battalion.
On 3 April, the U.S. asked for Turkey's support for the Manbij offensive, but the Turkish government made two demands in exchange for helping the international military intervention against ISIL; first, that the Syrian Arab tribes to be included in the Manbij operation should leave the SDF, and second, that the U.S. should increase its airstrikes in support of Turkish-backed Syrian rebels. On 4 April, according to a Turkish source, a group of U.S. military and intelligence staff traveled to Turkey to work on a plan for an operation to capture Manbij. The Turkish government later stated that it would not participate nor contribute to the offensive, because of the involvement of the Kurdish-majority People's Protection Units (YPG), and because it was beyond the range of artillery stationed in Turkey. When the offensive started, the Washington Post reported it under the headline of "Ignoring Turkey, U.S. backs Kurds in drive against ISIS in Syria".
On 5 April, a civilian council was formed in the town of Sarrin under the auspices of the Autonomous Administration of North and East Syria, of Manbij people who had fled when the Islamic State took over. The council consisted of Arabs, Kurds, Syrian Turkmen, and Circassians, and was created to administer Manbij after its capture. When international media interest in ethnic issues surged after the start of the offensive, Sheikh Farouk al-Mashi, an Arab former member of the Syrian parliament and designated co-chairman of the Manbij City Council, stated: "I have a Syrian ID, and Kurds have a Syrian ID. Let those people who talk against us in Turkey and Europe come here and fight ISIS. Why this distortion in media about problems between Kurds and Arabs?" Kurdish fellow co-chairman Salih Haji Mohammed stated: "In our social contract, we say we want to have good relations with neighboring countries like Turkey. Any country that does not interfere in Manbij and our areas, we will have good relations with."
On 31 May, the US announced that they would support the offensive and send supporting troops to the area. A US official stated that "Syrian Arab fighters would be the ones to stabilize and secure it once Islamic State is gone". The same day the offensive started, the Syrian Observatory for Human Rights (SOHR) stated "most of the fighters were from the Kurdish Popular Protection Units (YPG) militia". However, the next day, Turkish President Recep Tayyip Erdoğan said that around 3,000 SDF fighters were joining the operation and that some 2,500 of them were Arabs, while around 450 were from the YPG. Furthermore, two coalition spokesmen reiterated Arab fighters were leading the offensive, while Kurdish forces were in support, and one stated the reports that were suggesting the offensive was Kurdish-led were inaccurate. Another report stated, per local activists, that 60 percent of the attacking force were Arabs from Manbij. This was also confirmed by a MMC commander, who said that 60 percent of the attacking force were Arabs and 40 percent Kurds, Turkmen and other ethnic groups, while an SDF fighter gave his perspective as "we have Arabs, Kurds, nobody knows how many exactly, we all work under the SDF-forces".