During the biggest epic for Aleppo in 2016, the rebels, specifically the group of Jabhat Fat'h Al-Sham (JFS, HTS's core predecessor) captured the military faculties, namely the armament faculty and the adjacent faculty of tacticals - known in Arabic as:
كلية التسليح والكلية الفنية
The fighters showed great performance in holding their newly conquered position and inflicted great losses against a 5-nation army (the Assad's SAA, Lebanese hezbollah, iranian militias, iran-backed iraqi shia militia, and iran-backed afghan shia militia).
We see in the videos how a a determined resistance with well-trained artillery (that actually respects civilians as we could see they never targeted the enemy's gatherings in the city to avoid civilian casualties) and with little number of men can actually break humanly expectations and have the upper hand. They held the position for at least 2 weeks but eventually had to surrender after Russian jets launched their scorched-earth policy against Aleppo as the rebels were to able to break the tight siege which had been enforced by the Assad regime and its allies for 60 days (even before it there was a siege since 2012 but with less tightness as the vital Castello road was under rebels' control which provided a strategic conjunction between Aleppo's city and northern countryside so there was still room for supply flow), and after breaking the siege from the west and south they were practically few steps away from overtaking the entire city of Aleppo.
Video is compiled and edited by me. Music credits are to 'DOOM' and 'Metal Gear' video games.