Syrian rebels have breached the city of Aleppo, with thousands of insurgent fighters making startling advances in their surprise offensive against President Bashar al-Assad’s regime in northwestern Syria. The opposition rebels on Saturday made their way through large parts of the city, staking their claim in the very center of the city at the Aleppo Citadel and the Great Mosque of Aleppo, according to verified videos posted on social media. Videos circulating online on Friday appeared to show rebels in the outskirts of Aleppo, Syria’s second largest city.