Ukraine sent a 6,000 task force spearheading into Kursk and tried to hold a buffer for a period until the US election ended to secure longer-term support from the new US gov.
The incursion was a mistake in the first step, it was broadcast live everywhere on the web trying to portray a picture of Russia that could be defeated with a single blow. If everyone could see it, the Russians could see more.
Putin was enraged by such a kamikaze tactic and hence placed a clear order of total annihilation. Russia sent 3 counter-insurgent battle groups to go around the back to encircle the Ukrainian / NATO forces. Forcing them into landmine fields.
Up to 2 days ago, 3,500 were dead with 50 tanks and missile batteries destroyed. A field commanding post manned by Americans was encircled and burned to ashes. NATO tried again for a safe passage for the leftover troops to escape. We know how the intruders will end…

Reap what you sowed! Reap it!