High spring in Syria's largest city and the final battle has arrived. From his vantage point on a front line in Aleppo's northeast, Abu Bilal, a rebel commander, had spent the past month staring at a ridge line about a kilometer away that marked the closest Syrian military position.

A large white house, the one building still standing, had been the target for the only tank his men had. It shimmered in the rising heat and, at times, figures seemed to appear briefly in the distant haze. Were they really there?

There was nothing illusory about the Syrian soldiers and tanks that appeared last Thursday, though. Just after dawn, the ridge and the cobalt sky erupted with an intensity that Bilal and his unit had not seen in the 2-year-old fight for Aleppo.