ALEPPO, Syria — After almost a yearlong stalemate in Aleppo that hasn’t seen much in the way of significant gains for either side, the table is now being set for a major showdown. Although a serious regime offensive to retake Aleppo has been rumored on many previous occasions, this time it seems like it may be the real deal. Aside from small pieces of territory exchanging hands and intermittent clashes and skirmishes of varying ferocity, there has been nothing like the large-scale offensive recently launched by the regime in the southeast of Aleppo.

The regime’s rapid and successful takeover of the strategic town of Sfireh and nearby villages just to the south of Aleppo city has rebels visibly shaken. For too long they’ve been complacent and overconfident that their control over much of Aleppo province was unchallengeable. But a number of significant factors have changed this calculus and proved to be a rude awakening.

This has hastened a shotgun wedding of several major Islamist factions fighting in Aleppo in the name of the Islamic Front as well as a call to arms and a lockdown in areas of the city they control. A curfew was imposed, and the only crossing from rebel-held east Aleppo into the regime-held western part was permanently shut, which meant students couldn’t go to university and workers, especially civil servants, couldn’t get to their jobs. Residents of Aleppo now face the bizarre notion that to travel a few blocks from the east to the west of the city or vice versa, you had to travel about 500 kilometers (310.7 miles) down to Hama, then back up again through side roads and military routes, a journey of around 10 hours.

The rebels’ recent troubles started after Turkey tightened its border controls, particular after the Islamic State of Iraq and al-Sham (ISIS) took over adjacent territory. They were exacerbated by internal fighting, with ISIS going after various rebel brigades like Asefet el-Shamal, Ghuraba el-Sham and Shuhada Bader, which significantly weakened the rebels in the northern countryside and threatened to ignite a full scale interfactional war. All these are contributing factors to the rebels’ string of defeats, but the most significant one — not much talked about — is the defection of former rebels who helped the regime retake the strategic Mwasalat Haditha area.