What does the fall of Aleppo in the hands of the Syrian regime and its allies mean?

In the middle of international and regional inaction and fall back to provide support (which is originally limited) to the armed opposition in Syria and in the middle of a large Russian rush to fill the gap and achieve more gains by supporting the regime forces and its allies via direct air intervention, coinciding with looking forward to the mysterious new US policy in Trumps administration, opposition fighters were obliged to withdraw from eastern parts of Aleppo city after a long struggle with the regime forces and its allies inside the city which lasted about four years. This paper attempts to evaluate this incident from an analytical objective viewpoint.