Now here's where the speculation comes in, so bear with me... What if?

1. Prigozhin takes over military operations in Belarus and opens a new front with Ukraine.
2. Rumors are floating around that when the "Ukrainian Russian Patriot" brigade went across the border into Belgorod that they stole tactical nuclear weapons and brought them back to Ukraine. Probably artillery rounds if I had my guess.
3. Belarus attacks from the north with Prigozhin riding herd.
4. Ukraine supposedly "responds" to the attack by firing a tactical nuke at Belarus.
5. Belarus responds to the "Ukrainian nuclear attack" by nuking Kiev.
6. Russians can claim plausible deniability, because it was Belarus that fired off the nuke in "self-defense."
7. Russians look up from the chess board at the western leaders and say, "Check! Your move USA and Western Europe..."

I may be giving the Russian brain trust too much credit, but this is the kind of thing they would do and it would certainly make a good season of Jack Ryan.