Aleppo had been firmly held by the government since a 2016 victory there, one of the war's major turning points, when Russian-backed Syrian forces besieged and laid waste to rebel-held eastern areas of what had been the country's largest city.

Assad served as president since 2000 after taking over from his father, who ruled Syria for nearly three decades. Under the rule of the Assad family, Syria was widely characterize

It took just over a week for the 54-year Assad regime to fall in Syria and the Hayat Tahrir al-Sham rebel group to take control. WSJ breaks down how it happened—and what comes next for Syria and the Middle East.