they UC will need to create a large swath of land between both areas of the land bridge that is cut off, in order to feed/flood it with material, personnel, weaponry to defend the slice taken out of the land bridge throughout the winter. That and a few well targeted strikes to the bridge south of the Sea of Azov and Crimea will be West Berlin throughout the winter.
God I wish they had some planes, overwatch and JDAMS.
The front lines today are not going to be the front lines when the Rasputitsa starts. When mud season starts varies by where you are in the country. The further south you go the later it starts.
The Ukrainians have at least a month, quite possibly 6 weeks before it gets too muddy. They are moving around 2 Km a day now with the best Russian defensive line fully breached and the army in deteriorating condition. It's possible the Ukrainians will encounter some problem that will slow them down, but chances are that their pace will pick up as conditions deteriorate for the Russians. But assume they only get another month of good weather and only average 2 Km per day, that is still 60 Km. Tokmak is 90 Km from the Azov. Getting to only 30 Km from the Azov will allow Ukraine to virtually shut down traffic on the vital coastal road.
They could get to within 10 Km of the road (which runs inland several Km and the Ukrainians could average better than 2 Km per day). That puts the front lines well within 155mm artillery range of the road.
The Russians made a big effort to take the area at the border of Zapronizhia and Donestk last winter, losing a lot of vehicles, because the Ukrainians had the main rail line in the south under artillery interdiction there. Without that rail line they have been stuck to the roads, the main one being a very narrow highway that runs parallel to the coast.
I saw a video someone took near Mariupol a few months ago. The road is a narrow two lane highway and the westbound lanes were a solid traffic jam of civilian semi trucks crawling along.
Russia is in the same sort of problem Rommel had in North Africa. The road supply route has gotten very long and the trucks moving supplies are burning up most of the fuel. For the return trip the trucks need to be fueled from fuel already in theater which may have been moved by the trucks themselves.
Russia's supply lines for the south are very precarious and they are moving into a season where their non-ammunition supply requirements are going to skyrocket. In winter troops need more food, more shelter, and they burn fuel keeping warm. If those things aren't there, troops are going to be dying and getting injured from cold injuries (frostbite, trench foot, hypothermia, etc.) Good discipline for dealing with the cold and staying dry are vital to preventing these injuries, and the Russian army doesn't have that. The Russians may not care about the well being of its troops, but the cold will sap their manpower as badly as a major battle.
On the other side the Ukrainians have good cold weather discipline and their cold injuries last winter were vastly lower than Russia.
Retrospectively, the Ukrainian counteroffensive approach seems to have been the wisest.
Many hoped for a massive counteroffensive from the get-go. But it seems clear the approach of first softening Russian defensive positions with weeks of destruction of ammunition/fuel depots, air-defenses, artillery, tanks, command centers, air bases, supply lines, carefully mapping out ways through mine fields, etc., was the right approach. This saved many Ukrainian lives they will need for a long game scenario towards victory and continue to have sufficient manpower.
The Ukrainians have done well with what they had. NATO would have done things differently, but NATO has a different mix of resources. Ukraine has a hand-me-down army with whatever equipment the world gave them. They have suffered supply shortages and some weapons common in the NATO arsenal (mostly aircraft) are in short supply and will remain in short supply.
There has been so much talk about Russia having a larger population. Ukraine fully mobilized at the start of the war. There is very little economy going on that is not focused on the war in one way or another. The agricultural sector is still trying to grow as much as possible, but that's also in furtherance of the war effort. Ukraine has taken anyone fit for service, including women. Ukraine does not need to make all their weapons and supplies. A large portion is coming from other countries. Ukraine is also united behind the war effort. The number of Ukrainians who think it would be a good thing to let Russia take over Ukraine is very small and they are mostly keeping quiet about it. Ukraine evacuated most of the population who couldn't contribute to the war in the first weeks of the war and most of those people are still living in Europe.
On the other hand Russia has tried to keep their civilian economy going, they need to make virtually all their own supplies with few allies. Where Russia is getting supplies from outside Russia they are paying for them. Russia needs to keep the economy going well enough to pay for the supplies they are importing as well as the supplies they are making themselves. The people of Russia are not behind the war. Most are just keeping quiet and hoping it doesn't affect them too badly.
Because of Russia's inverted population pyramid, they have a large elderly older population that needs to be supported by a small cadre of young working people. Their army is exclusively male. The population that isn't contributing to the war effort are still in Russia drawing resources and needing workers to support.
Russia has about 8 million men between 18 and 30. Most of those men are required to keep the economy going. They can't spare a large portion of them to go to war. A lot of them left the country to avoid being drafted. Most of those who left are the most capable of that generation. If Russia tried to do a mass mobilization to outnumber the Ukrainian army they would end up crippling their civilian economy to do so. Additionally they are struggling to find enough uniforms and small arms for the mobiks they have now. The Ukrainians have been capturing WW II era small arms as they take territory. Lot's of Russia soldiers have been seen on the front lines wearing civilian sports shoes instead of boots and their uniforms are a mishmash of whatever they found in the back of the warehouse.
Russia is physically capable of creating a force of a few million, but their economy would collapse, the army would be wearing Adidas track suits, and they would be armed with sticks.
The Ukrainians have also been vastly better at force preservation. They take fewer risks with lives, and their medical evac is vastly better. The Russians have thrown away lives right and left in their attempts to keep what they captured in the first days of the war. Russian medical evac and field medicine is poorer than what the western Allies had in 1943. Their troops are not training in first aid so when they do give first aid, the do it wrong so a lot of people die from shock or lose limps that could have been saved.
The Ukrainians by evacuating the wounded and doing the best they can to restore all wounded to full health not only helps morale, but it also helps preserve the force and help it get better. Someone who was badly wounded and becomes unable to fight can still be an instructor who imparts what they learned on the trainee soldiers. The disabled can also take rear area jobs that don't require a lot of physical ability. Ukraine needs thousands of drone operators and there are lots of other jobs they can do. This frees up more fit people for the front lines.
As of a few months ago Ukraine had an estimated 800,000-1.2 million people in uniform. Ukraine has done all it can to keep casualties down and return the wounded to the service if possible.
Nobody knows for sure how many people Russia has in Ukraine. I'm not sure the Kremlin has a good idea. Because of rampant lying from commanders, the reports for unit strength are more fiction than fact. We know from intercepted phone calls and videos people have put on Telegram that quite a few Russian units are nothing more than shells with only a handful of troops.
I would say the absolute maximum Russia has in Ukraine, or dedicated to Ukraine (support near Ukraine's borders) is about 300,000. It could be as low as 100,000. This includes all the troops dedicated to supporting their aviation, naval forces, manning the air defenses, and moving supply. That leaves a thin force left to defend a very long front.
Ukraine could have taken heavy losses and done a full scale assault on the first line of defenses, but they chose to preserve their forces and do a more nuanced approach that took more time. Ultimately that's better for Ukraine. Having more people survive the first line of defense attacks leaves them with more forces to go after the next line. Additionally there is also the humanitarian angle, it's always a good idea to preserve the lives of your people for the sake of the people themselves.