Declaring that WW3 has started is nonsense. If this does descend into WW3 it will indeed be possible (if anyone is left alive) to trace the start back to some time in the past, but you're taking it as read that it's not possible for this to de-escalate and not end up with WW3 in the next few decades (or whatever timeframe you're choosing).Well WW3 has already started before 2014. Whether you believe there is a Gerasimov Doctrine or not, the hybrid phase of the war has been going on for over 8 years. And here we are now with soldiers fighting in trenches.
Even a peace deal in Ukraine only pauses this phase of WW3.