russia began the war by massing tanks, and having huge armored columns attack. They used this tactic as late as Avdiivka.
Around Kyiv, at the start of the war, Ukraine would take out the front and rear vehicle of a column, and then the rest of the column was picked off. This was usually done with massed artillery or Javelins/NLAWs. Later on drones started to be used for this. russia also struggled with modern tank tactics. They were sending solo tanks into cities, without an infantry escort, where they would get picked off by ATGMs.
This was easier to accomplish because roads into Kyiv from Belarus are limited, due to rivers and bridges.
For places like Avdiivka, fortifications would funnel the mechanized columns into kill zones. This made it easier for recon drones to spot them, and then artillery would strike them. Ukraine claims 364 tanks and 748 armored fighting vehicles were lost there.
Kofman described this war as “the last war of the Soviet Union” because after russia lost too many modern tanks, they refurbished as much as they could from USSR stockpiles, and have lost those as well.
Ukraine also had 3 major defensive positions in Avdiivka which allowed them to contest a massive attacks with a relatively small force. These are the closest to what one normally thinks when the word “fortifications” gets used. The biggest fortification was a Coke plant, which had underground shelters and was made of thick concrete, which helped protect against glide bombs, artillery and drones.
The fall of this fortified area is largely why we are seeing russia advancing into Pokrovsk. If Ukraine has more fortified positions behind Avdiivka, they would probably be losing less territory and also inflicting more casualties.
The current method of russian advances that we’re seeing is a recent adaption. Artillery played a huge role at the start of the war, and there was a major focus on getting Ukraine enough shells to repel russia’s massing tactics. russia responded to the shortage of shells, increased recon drones, and struggling to advance with mechanized units, by sending infantry in smaller groups, making it inefficient to use an expensive 155mm shell to kill them. Ukraine adapted to this by scaling up drone manufacturing, dropping mines using drones, and putting obstacles to funnel the russians into chokepoints for drones to pick off more easily.
russia is now responding by sending russian infantry in even smaller groups, usually not engaging even when they do see Ukrainian infantry, and instead focusing on trying to get as far as possible, grouping up, and then contesting that area. These fortifications seem like an adaptation to that: everything is cleared so infantry has to walk with absolutely no cover, they then have to pass barbed wire and a minefield. Even if they are able to take control of the area where these fortifications are, any logistics are forced through chokepoints which Ukraine can strike with drones even after they are pushed back.
Here’s a close up image of one of the lines, it looks like there’s several layers of this:
Only likely if there’s a peace deal - less chance than the US invading Greenland