The Kremlin said on Monday that the only way to protect Russian territory from Ukrainian attacks was to create a buffer zone that would put Russian regions beyond the range of Ukrainian fire. The Kremlin was commenting after President Vladimir Putin raised the possibility of setting up such a zone in a speech after winning re-election on Sunday.
I picture a military buffer zone as something like what separates the Koreas. Otoh Israel used similar reasoning when initially justifying its seizure of the occupied territories, and this is looking a lot more like the latter. (Ironically, they are now talking about a buffer zone with Gaza. They need a buffer zone for a buffer zone.)