Despite months of preparation, the Syrian rebels' last-ditch effort to break the loyalist siege on Aleppo appears to be on the verge of failure. The offensive, which began Oct. 28, involved an unprecedented level of collaboration among an array of rebel groups with disparate ideologies. As the rebels came to the aid of their beleaguered peers in eastern Aleppo, they made quick progress -- at least initially. After three days, however, the rebels' steady advance stalled, and by Nov. 6 they once again found themselves fending off a barrage of withering loyalist attacks....