We can look at October 7th in Israel how long, with all the communications and infrastructure working, it took to organize defense in a very technologically developed country which basically had been living in the state of war readiness. Now add broken significant communications, chaos of non-working banks/ATMs, power shut-offs, clogged highways, etc. (don't get me wrong - i'm not saying that Russia can do all that, i'm saying that Russia is actively working on those capabilities, and whether they achieve it to the needed extent is the key to how the events would go in the near future)