Why counter attack (with the majority of forces) right away? Russians have shown poorer abilities when organizing offensives compared to defending. The incursion into Russia by Ukraine forces the Russian military into attacking. This is as opposed to sitting behind a thousand minefields in unmoving lines inside Ukraine.
Ukraine can set up elaborate layered defenses and enjoy the defensive advantage to grind up more Russian military assets. This also gives Ukraine opportunities for small detachments to hit the Russian reinforcements on the move, which is something they’ve already been doing.
If I read it correctly, Ukraine is facing a very large force to the north and struggling to repel it. If you open up another front, you force Putin to hopefully take troops from there to use on the defence in Kursk, thereby lessening the load on the soldiers defending in the North.
Peeling off Russian forces is exactly what Ukraine has already done with this force. I believe it was entirely the point.
Russia is forced not to ignore this for numerous reasons, and it forces them to attack to expel the Ukrainian forces. Successfully attacking with conscripts is a more difficult proposition than defending.
Ukrainian forces inside Russia can continue to force the confrontation by advancing into undefended territory and/or launching limited small scale attacks to be a constant wound inside of Russia. Ukrainians have already been conducting these attacks on reinforcements on their way to stop the main Ukrainian forces.
All the while Ukrainians inside Russia can refuse to assault defended positions. Which is exactly what they did initially. They bypassed the heavy positions and refused to engage in heavy force on force assaults. Instead as local defenders they are creating a lopsided local situation.
As an aside, where are Russian air assets? Inside Ukraine the skies were contested, but the apparent inability of air assets to repel Ukrainians from Russian territory with air power is not a good sign for Russia.
From what I read, the incursion force brought AA, making it hard for Russian air. Moreover, they did strike a few nearby airfields.
