As the Russians close in on Grozny, the difficult truth is that there is almost certainly nothing we can do to avert the onslaught. If western countries were to immediately announce the fullest range of sanctions on Russia, the attacks would go ahead all the same. They would only be called off if Russia had some powerful reason of her own to do so, and none is visible. There might be a sliver of a chance of a reprieve if the deadline were extended and the Chechen government offered talks in which the withdrawal of Chechen extremists would be the first item for discussion, but that is inherently unlikely. Western forbearance and attempts at quiet persuasion would be, and have been, similarly unproductive.
Russian policy is, in the short term, unalterable.
But, in the longer term, the west can help shape a saner attitude in both Moscow and Grozny. That is indeed their only hope, and ours too, since Chechnya is a conflict with a potentially destructive impact not only in the Caucasus and Russia but anywhere in the world where minorities are at harsh odds with central governments. Certainly, more should have been done at an earlier stage. The likely side effects should give anyone pause. Trying to bring in legal international sanctions would probably wreck both the United Nations and the west's whole relationship with Russia.