It is now about a month ago that Iraq started its offensive to retake Mosul from ISIS - with the support of the US.
From the beginning it has appeared as a weird operation to me. There was just too much territory around Mosul that needed to be conquered first. And they weren't even close to surrounding the city. It looks to me as a politically motivated operation - most likely Obama wants to have this finished before he hands over power to Trump. He must be well aware that the fall of Mosul - and his initial passive reaction to it - are among the biggests errors of his heritage.
But while it may make political sense it doesn't make much military sense. As it is unlikely that the ISIS defenses will break down it means that increasingly exhausted troops may increasingly get stuck in ISIS defenses.
The normal logic of a military offensive is that you assemble a lot of troops and material at one of a few locations so that at that location your forces are clearly superior to those of your enemy. Then you overrun his defenses and look how far you can come. However, unless the enemy defenses totally collapse you will find after a couple of days that your numeric superiority has evaporated and that you are suffering increasingly heavy losses against a well entrenched enemy. It is then time to stop and resupply and to consider what would be the best location and tactic for the next attack.
It looks like in Mosul that rhythm has been broken by the pressure for military success. There seems to be no strategy at all. It is attacking on all fronts and keeping attacking. And yet Tel Afar on the supply line of ISIS to Syria is protected by Turkey. Rumors are that already 3500 anti-ISIS fighters died. ISIS members who flee towards Syria are left unharmed. Very little is done to bridge the gap between Sunnites and Shiites.
Compare this to what is happening in Aleppo. First the government surrounded East Aleppo. Then it took some time to conquer the North of that area, a mainly industrial area that was relatively easy to conquer. Then it mainly let the siege do its own work and focused on the area to the West of Aleppo while keeping the pressure up in the East with occasional attacks and threats.
It is generally expected that it is a matter of time before the rebels lose East Aleppo. For Mosul the scenario is less clear. If ISIS is driven out it may well be a matter of brute force with a lot of American involvement that will leave the city devastated. Unlike the Russians in Syria the US in Iraq seems unable to forge a broad alliance that can provide future stability.