IS took over all levels of civil administration, rewriting school curriculums, establishing Islamic courts and creating police units to implement Islamic law.
In April a documentary claimed the world's most wanted man, who has a bounty of A$34 million on his head, avoided capture by Iraqi special forces "by minutes" after escaping through a trapdoor.
That revelation came just days after al-Baghdadi's deputy Ayad al-Jumaili was killed in an air strike.
In March US and Iraq authorities believed al-Baghdadi had abandoned his fighters and gone into hiding as Iraqi forces continued to make inroads into Mosul,
Raqqa also became the scene of some of IS's worst atrocities, including gruesome executions, public displays of bodies and sex trafficking.
The city has long been seen as a prize by multiple parties to the Syrian conflict, including the government, Russia, Turkey and the US-led coalition bombing IS since 2014.
On November 5 last year, the Syrian Democratic Forces (SDF), a US-backed Arab-Kurdish alliance, launched a major offensive dubbed "Wrath of the Euphrates" to take Raqqa.
An estimated 300,000 civilians were believed to have been living under IS rule in Raqqa, including 80,000 who fled there from other parts of the country.
But as the SDF drew closer to the city, thousands were smuggled out to territory newly captured by the US-backed fighters.
After a string of victories in the surrounding province, including the key town of Tabqa and the adjacent dam, the SDF has sealed off the approaches to Raqqa city from the north, east and west.
On Tuesday, the SDF said its forces entered the city from the eastern district of Al-Meshleb.
The US-led coalition has been backing the SDF with air strikes, equipment and special forces advisers.
On Monday, a coalition bombing raid killed 21 civilians as they tried to escape Raqqa by dinghy on the Euphrates River, a route also used by IS fighters, the Syrian Observatory for Human Rights said.
More to come ...
